leetcode-next

https://github.com/Overhellz/leetcode-next

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Leetcode Badges

Top Interview 150

https://leetcode.com/studyplan/top-interview-150/

Top 100 Liked

https://leetcode.com/studyplan/top-100-liked/

LeetCode 75

https://leetcode.com/studyplan/leetcode-75/

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Retention	Description
5	Решено самостоятельно, в пределах времени.
4	Решено самостоятельно, но слишком медленно / незначительные ошибки.
3	Вспомнил алгоритм, но в коде были ошибки / нужны были подсказки.
2	Смутно помнил тему, не смог решить.
1	Полный провал (не распознал задачу).

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1. Fundamentals

1. Array / String
2. Two Pointers
3. Sliding Window
4. Hash Map
5. Stack, Queue
6. Prefix Sum
7. Binary Search
8. Intervals

2. Linked Lists & Trees

1. Linked List
2. Binary Tree DFS
3. Binary Tree BFS
4. Binary Search Tree BST
5. Trie
6. Heap / Priority Queue

3. Graphs

1. Graph General
2. Graph DFS
3. Graph BFS
4. Topological Sort
5. Dijkstra's Algorithm (Shortest Path)
6. Union-Find (Disjoint Set)

4. Recursion & Combinatorics

1. Recursion basics
2. Backtracking
   • Subsets
   • Combinations
   • Permutations
   • Subsets with duplicates
   • Combination sum
   • Palindrome partitioning
   • N-Queens
3. Divide & Conquer
   • Merge sort
   • Quick select (Kth largest)

5. Dynamic Programming

1. DP — Memoization vs Tabulation
2. DP — 1D
   • Climbing stairs
   • House robber
   • Decode ways
   • Word break
3. DP — 2D
   • Unique paths
   • Longest common subsequence
   • Edit distance
   • Coin change II
4. DP — Interval / Matrix
   • Palindrome substrings
   • Burst balloons (optional)
5. DP — State machine
   • Best time to buy/sell stock (with cooldown, transaction limits)

6. Advanced / Complementary

1. Greedy Algorithms
   • Interval scheduling
   • Jump game
   • Gas station
2. Bit Manipulation
   • XOR tricks
   • Bit masking for subsets
3. Monotonic Stack
   • Next greater element
   • Largest rectangle in histogram
4. Design / OOP
   • LRU Cache (if asked)
   • Min stack
   • Randomized set

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1 Fundamentals

1.1 Array / String

Level	Name	Link	Retention
Easy	1768. Merge Strings Alternately	https://leetcode.com/problems/merge-strings-alternately/
Easy	1071. Greatest Common Divisor of Strings	https://leetcode.com/problems/greatest-common-divisor-of-strings/
Easy	1431. Kids With the Greatest Number of Candies	https://leetcode.com/problems/kids-with-the-greatest-number-of-candies/
Easy	605. Can Place Flowers	https://leetcode.com/problems/can-place-flowers/
Easy	345. Reverse Vowels of a String	https://leetcode.com/problems/reverse-vowels-of-a-string/
Medium	334. Increasing Triplet Subsequence	https://leetcode.com/problems/increasing-triplet-subsequence/
Medium	443. String Compression	https://leetcode.com/problems/string-compression/

1.2 Two Pointers

Level	Name	Link	Retention
Easy	283. Move Zeroes	https://leetcode.com/problems/move-zeroes/
Medium	1679. Max Number of K-Sum Pairs	https://leetcode.com/problems/max-number-of-k-sum-pairs/
Easy	344. Reverse String	https://leetcode.com/problems/reverse-string/
Easy	977. Squares of a Sorted Array	https://leetcode.com/problems/squares-of-a-sorted-array/
Easy	844. Backspace String Compare	https://leetcode.com/problems/backspace-string-compare/
Medium	18. 4Sum	https://leetcode.com/problems/4sum/

1.3 Sliding Window

Level	Name	Link	Retention
Easy	643. Maximum Average Subarray I	https://leetcode.com/problems/maximum-average-subarray-i/
Medium	1004. Max Consecutive Ones III	https://leetcode.com/problems/max-consecutive-ones-iii/
Medium	1493. Longest Subarray of 1's After Deleting One Element	https://leetcode.com/problems/longest-subarray-of-1s-after-deleting-one-element/
Medium	904. Fruit Into Baskets	https://leetcode.com/problems/fruit-into-baskets/
Medium	424. Longest Repeating Character Replacement	https://leetcode.com/problems/longest-repeating-character-replacement/
Medium	567. Permutation in String	https://leetcode.com/problems/permutation-in-string/
Medium	438. Find All Anagrams in a String	https://leetcode.com/problems/find-all-anagrams-in-a-string/
Hard	239. Sliding Window Maximum	https://leetcode.com/problems/sliding-window-maximum/
Medium	1456. Maximum Number of Vowels in a Substring of Given Length	https://leetcode.com/problems/maximum-number-of-vowels-in-a-substring-of-given-length/

1.4 Hash Map

Level	Name	Link	Retention
Easy	706. Design HashMap	https://leetcode.com/problems/design-hashmap/
Easy	136. Single Number	https://leetcode.com/problems/single-number/
Medium	49. Group Anagrams	https://leetcode.com/problems/group-anagrams/
Medium	454. 4Sum II	https://leetcode.com/problems/4sum-ii/

1.5 Stack, Queue

Level	Name	Link	Repeatable
Easy	1047. Remove All Adjacent Duplicates In String	https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/
Medium	2390. Removing Stars From a String	https://leetcode.com/problems/removing-stars-from-a-string/
Easy	933. Number of Recent Calls	https://leetcode.com/problems/number-of-recent-calls/
Easy	20. Valid Parentheses	https://leetcode.com/problems/valid-parentheses/
Easy	1047. Remove All Adjacent Duplicates In String	https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/
Medium	2390. Removing Stars From a String	https://leetcode.com/problems/removing-stars-from-a-string/
Easy	232. Implement Queue using Stacks	https://leetcode.com/problems/implement-queue-using-stacks/
Easy	225. Implement Stack using Queues	https://leetcode.com/problems/implement-stack-using-queues/
Easy	933. Number of Recent Calls	https://leetcode.com/problems/number-of-recent-calls/
Medium	71. Simplify Path	https://leetcode.com/problems/simplify-path/

1.6 Prefix Sum

Level	Name	Link	Retention
Easy	303. Range Sum Query - Immutable	https://leetcode.com/problems/range-sum-query-immutable/
Easy	724. Find Pivot Index	https://leetcode.com/problems/find-pivot-index/
Medium	560. Subarray Sum Equals K	https://leetcode.com/problems/subarray-sum-equals-k/
Medium	525. Contiguous Array	https://leetcode.com/problems/contiguous-array/
Medium	974. Subarray Sums Divisible by K	https://leetcode.com/problems/subarray-sums-divisible-by-k/

1.7 Binary Search

Level	Name	Link	Retention
Easy	704. Binary Search	https://leetcode.com/problems/binary-search/	5
Easy	35. Search Insert Position	https://leetcode.com/problems/search-insert-position/	3
Medium	34. Find First and Last Position of Element in Sorted Array	https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/	2
Medium	74. Search a 2D Matrix	https://leetcode.com/problems/search-a-2d-matrix/	3
Medium	153. Find Minimum in Rotated Sorted Array	https://leetcode.com/problems/find-minimum-in-rotated-sorted-array/	2
Medium	33. Search in Rotated Sorted Array	https://leetcode.com/problems/search-in-rotated-sorted-array/	2
Medium	162. Find Peak Element	https://leetcode.com/problems/find-peak-element/	2
Medium	875. Koko Eating Bananas	https://leetcode.com/problems/koko-eating-bananas/	2

1.8 Intervals

Level	Name	Link	Retention
Medium	56. Merge Intervals	https://leetcode.com/problems/merge-intervals/
Medium	57. Insert Interval	https://leetcode.com/problems/insert-interval/
Medium	435. Non-overlapping Intervals	https://leetcode.com/problems/non-overlapping-intervals/
Medium	452. Minimum Number of Arrows to Burst Balloons	https://leetcode.com/problems/minimum-number-of-arrows-to-burst-balloons/
Medium	986. Interval List Intersections	https://leetcode.com/problems/interval-list-intersections/
Medium(-)	763. Partition Labels	https://leetcode.com/problems/partition-labels/
Medium	2406. Divide Intervals Into Minimum Number of Groups	https://leetcode.com/problems/divide-intervals-into-minimum-number-of-groups/
Medium	1288. Remove Covered Intervals	https://leetcode.com/problems/remove-covered-intervals/

2 Linked Lists & Trees

2.1 Linked List

Level	Name	Link	Retention
Medium	707. Design Linked List	https://leetcode.com/problems/design-linked-list/
Easy	876. Middle of the Linked List	https://leetcode.com/problems/middle-of-the-linked-list/
Medium	2095. Delete the Middle Node of a Linked List	https://leetcode.com/problems/delete-the-middle-node-of-a-linked-list/
Easy	206. Reverse Linked List	https://leetcode.com/problems/reverse-linked-list/
Easy	234. Palindrome Linked List	https://leetcode.com/problems/palindrome-linked-list/
Easy	83. Remove Duplicates from Sorted List	https://leetcode.com/problems/remove-duplicates-from-sorted-list/
Medium	19. Remove Nth Node From End of List	https://leetcode.com/problems/remove-nth-node-from-end-of-list/
Medium	24. Swap Nodes in Pairs	https://leetcode.com/problems/swap-nodes-in-pairs/
Easy	21. Merge Two Sorted Lists	https://leetcode.com/problems/merge-two-sorted-lists/
Easy	141. Linked List Cycle	https://leetcode.com/problems/linked-list-cycle/
Medium	146. LRU Cache	https://leetcode.com/problems/lru-cache/
Easy	206. Reverse Linked List	https://leetcode.com/problems/reverse-linked-list/
Easy	21. Merge Two Sorted Lists	https://leetcode.com/problems/merge-two-sorted-lists/
Easy	141. Linked List Cycle	https://leetcode.com/problems/linked-list-cycle/
Medium	142. Linked List Cycle II	https://leetcode.com/problems/linked-list-cycle-ii/
Medium	876. Middle of the Linked List	https://leetcode.com/problems/middle-of-the-linked-list/
Medium	19. Remove Nth Node From End of List	https://leetcode.com/problems/remove-nth-node-from-end-of-list/
Medium	2. Add Two Numbers	https://leetcode.com/problems/add-two-numbers/
Medium	234. Palindrome Linked List	https://leetcode.com/problems/palindrome-linked-list/
Medium	143. Reorder List	https://leetcode.com/problems/reorder-list/
Medium	138. Copy List with Random Pointer	https://leetcode.com/problems/copy-list-with-random-pointer/
Medium	24. Swap Nodes in Pairs	https://leetcode.com/problems/swap-nodes-in-pairs/

2.2 Binary Tree DFS

Level	Name	Link	Retention
Easy	104. Maximum Depth of Binary Tree	https://leetcode.com/problems/maximum-depth-of-binary-tree/
Easy	226. Invert Binary Tree	https://leetcode.com/problems/invert-binary-tree/
Easy	100. Same Tree	https://leetcode.com/problems/same-tree/
Easy	101. Symmetric Tree	https://leetcode.com/problems/symmetric-tree/
Easy	112. Path Sum	https://leetcode.com/problems/path-sum/
Easy	104. Maximum Depth of Binary Tree	https://leetcode.com/problems/maximum-depth-of-binary-tree/
Easy	226. Invert Binary Tree	https://leetcode.com/problems/invert-binary-tree/
Medium	100. Same Tree	https://leetcode.com/problems/same-tree/
Medium	101. Symmetric Tree	https://leetcode.com/problems/symmetric-tree/
Easy	112. Path Sum	https://leetcode.com/problems/path-sum/
Medium	543. Diameter of Binary Tree	https://leetcode.com/problems/diameter-of-binary-tree/
Medium	236. Lowest Common Ancestor of a Binary Tree	https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/
Medium	105. Construct Binary Tree from Preorder and Inorder Traversal	https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/
Medium	114. Flatten Binary Tree to Linked List	https://leetcode.com/problems/flatten-binary-tree-to-linked-list/

2.3 Binary Tree BFS

Level	Name	Link	Retention
Medium	102. Binary Tree Level Order Traversal	https://leetcode.com/problems/binary-tree-level-order-traversal/
Medium	515. Find Largest Value in Each Tree Row	https://leetcode.com/problems/find-largest-value-in-each-tree-row/
Medium	199. Binary Tree Right Side View	https://leetcode.com/problems/binary-tree-right-side-view/
Medium	117. Populating Next Right Pointers in Each Node II	https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/
Medium	236. Lowest Common Ancestor of a Binary Tree	https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/
Medium	1325. Delete Leaves With a Given Value	https://leetcode.com/problems/delete-leaves-with-a-given-value/
Medium	1302. Deepest Leaves Sum	https://leetcode.com/problems/deepest-leaves-sum/
Easy	543. Diameter of Binary Tree	https://leetcode.com/problems/diameter-of-binary-tree/
Medium	103. Binary Tree Zigzag Level Order Traversal	https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
Easy	637. Average of Levels in Binary Tree	https://leetcode.com/problems/average-of-levels-in-binary-tree/	-
Medium	102. Binary Tree Level Order Traversal	https://leetcode.com/problems/binary-tree-level-order-traversal/
Medium	103. Binary Tree Zigzag Level Order Traversal	https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
Medium	199. Binary Tree Right Side View	https://leetcode.com/problems/binary-tree-right-side-view/
Medium	515. Find Largest Value in Each Tree Row	https://leetcode.com/problems/find-largest-value-in-each-tree-row/
Medium	513. Find Bottom Left Tree Value	https://leetcode.com/problems/find-bottom-left-tree-value/
Medium	1302. Deepest Leaves Sum	https://leetcode.com/problems/deepest-leaves-sum/
Medium	117. Populating Next Right Pointers in Each Node II	https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/
Medium	116. Populating Next Right Pointers in Each Node	https://leetcode.com/problems/populating-next-right-pointers-in-each-node/
Medium	987. Vertical Order Traversal of a Binary Tree	https://leetcode.com/problems/vertical-order-traversal-of-a-binary-tree/	1

2.4 Binary Search Tree BST

Level	Name	Link	Retention
Easy	700. Search in a Binary Search Tree	https://leetcode.com/problems/search-in-a-binary-search-tree/
Medium	701. Insert into a Binary Search Tree	https://leetcode.com/problems/insert-into-a-binary-search-tree/
Medium	98. Validate Binary Search Tree	https://leetcode.com/problems/validate-binary-search-tree/
Easy	110. Balanced Binary Tree	https://leetcode.com/problems/balanced-binary-tree/
Easy	700. Search in a Binary Search Tree	https://leetcode.com/problems/search-in-a-binary-search-tree/
Easy	108. Convert Sorted Array to Binary Search Tree	https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
Medium	98. Validate Binary Search Tree	https://leetcode.com/problems/validate-binary-search-tree/
Easy	110. Balanced Binary Tree	https://leetcode.com/problems/balanced-binary-tree/
Medium	701. Insert into a Binary Search Tree	https://leetcode.com/problems/insert-into-a-binary-search-tree/
Medium	450. Delete Node in a BST	https://leetcode.com/problems/delete-node-in-a-bst/
Medium	230. Kth Smallest Element in a BST	https://leetcode.com/problems/kth-smallest-element-in-a-bst/
Medium	173. Binary Search Tree Iterator	https://leetcode.com/problems/binary-search-tree-iterator/
Medium	538. Convert BST to Greater Tree	https://leetcode.com/problems/convert-bst-to-greater-tree/

2.5 Trie

Level	Name	Link	Retention
Medium	208. Implement Trie (Prefix Tree)	https://leetcode.com/problems/implement-trie-prefix-tree/
Medium	1268. Search Suggestions System	https://leetcode.com/problems/search-suggestions-system/

2.6 Heap

Level	Name	Link	Retention
Medium	215. Kth Largest Element in an Array	https://leetcode.com/problems/kth-largest-element-in-an-array/
Easy	703. Kth Largest Element in a Stream	https://leetcode.com/problems/kth-largest-element-in-a-stream/
Medium	347. Top K Frequent Elements	https://leetcode.com/problems/top-k-frequent-elements/
Medium	451. Sort Characters By Frequency	https://leetcode.com/problems/sort-characters-by-frequency/
Easy	1046. Last Stone Weight	https://leetcode.com/problems/last-stone-weight/
Hard	502. IPO	https://leetcode.com/problems/ipo/
Hard	295. Find Median from Data Stream	https://leetcode.com/problems/find-median-from-data-stream/
Medium	1962. Remove Stones to Minimize the Total	https://leetcode.com/problems/remove-stones-to-minimize-the-total/
Hard	23. Merge k Sorted Lists	https://leetcode.com/problems/merge-k-sorted-lists/

3 Graphs

3.1 Graph General

Level	Name	Link	Retention
Medium	841. Keys and Rooms	https://leetcode.com/problems/keys-and-rooms/
Medium	1971. Find if Path Exists in Graph	https://leetcode.com/problems/find-if-path-exists-in-graph/
Medium	133. Clone Graph	https://leetcode.com/problems/clone-graph/
Medium	1557. Minimum Number of Vertices to Reach All Nodes	https://leetcode.com/problems/minimum-number-of-vertices-to-reach-all-nodes/

3.2 Graph DFS

Level	Name	Link	Retention
Medium	547. Number of Provinces	https://leetcode.com/problems/number-of-provinces/
Medium	200. Number of Islands	https://leetcode.com/problems/number-of-islands/
Medium	1466. Reorder Routes to Make All Paths Lead to the City Zero	https://leetcode.com/problems/reorder-routes-to-make-all-paths-lead-to-the-city-zero/
Medium	695. Max Area of Island	https://leetcode.com/problems/max-area-of-island/
Medium	2368. Reachable Nodes With Restrictions	https://leetcode.com/problems/reachable-nodes-with-restrictions/
Medium	542. 01 Matrix	https://leetcode.com/problems/01-matrix/

3.3 Graph BFS

Level	Name	Link	Retention
Medium	1129. Shortest Path with Alternating Colors	https://leetcode.com/problems/shortest-path-with-alternating-colors/
Medium	1926. Nearest Exit from Entrance in Maze	https://leetcode.com/problems/nearest-exit-from-entrance-in-maze/
Medium	1091. Shortest Path in Binary Matrix	https://leetcode.com/problems/shortest-path-in-binary-matrix/
Medium	752. Open the Lock	https://leetcode.com/problems/open-the-lock/
Medium	433. Minimum Genetic Mutation	https://leetcode.com/problems/minimum-genetic-mutation/
Medium	994. Rotting Oranges	https://leetcode.com/problems/rotting-oranges/

3.4 Dijkstra

Level	Name	Link	Retention
Medium	743. Network Delay Time	https://leetcode.com/problems/network-delay-time/
Medium	1514. Path with Maximum Probability	https://leetcode.com/problems/path-with-maximum-probability/
Medium	787. Cheapest Flights Within K Stops	https://leetcode.com/problems/cheapest-flights-within-k-stops/

3.5 Topological sort

Level	Name	Link	Retention
Medium	2115. Find All Possible Recipes from Given Supplies	https://leetcode.com/problems/find-all-possible-recipes-from-given-supplies/
Medium	207. Course Schedule	https://leetcode.com/problems/course-schedule/
Medium	210. Course Schedule II	https://leetcode.com/problems/course-schedule-ii/

Backtracking

Level	Name	Link	Retention
Medium	46. Permutations	https://leetcode.com/problems/permutations/
Medium	77. Combinations	https://leetcode.com/problems/combinations/
Medium	78. Subsets	https://leetcode.com/problems/subsets/
Medium	22. Generate Parentheses	https://leetcode.com/problems/generate-parentheses/
Medium	216. Combination Sum III	https://leetcode.com/problems/combination-sum-iii/
Medium	17. Letter Combinations of a Phone Number	https://leetcode.com/problems/letter-combinations-of-a-phone-number/
Hard	51. N-Queens	https://leetcode.com/problems/n-queens/
Hard	489. Robot room cleaner	https://leetcode.com/problems/robot-room-cleaner/
Easy	257. Binary Tree Paths	https://leetcode.com/problems/binary-tree-paths/	2
Medium	784. Letter Case Permutation	https://leetcode.com/problems/letter-case-permutation/	2
Medium	78. Subsets	https://leetcode.com/problems/subsets/	2
Medium	46. Permutations	https://leetcode.com/problems/permutations/
Medium	39. Combination Sum	https://leetcode.com/problems/combination-sum/
Medium	17. Letter Combinations of a Phone Number	https://leetcode.com/problems/letter-combinations-of-a-phone-number/
Medium	22. Generate Parentheses	https://leetcode.com/problems/generate-parentheses/
Medium	79. Word Search	https://leetcode.com/problems/word-search/
Medium	90. Subsets II	https://leetcode.com/problems/subsets-ii/
Medium	77. Combinations	https://leetcode.com/problems/combinations/

Топ-8 задач Backtracking для собеседования (80% покрытия) № Уровень Название Суть задачи (почему она популярна) 1 Medium 78. Subsets Классика. Сгенерировать все возможные подмножества. Это базовая задача на "Decision Tree", где нужно решать: брать элемент или не брать. 2 Medium 46. Permutations Классика. Сгенерировать все перестановки массива [citations:1][citations:6]. Проверяет, как вы управляете "посещенными" элементами. 3 Medium 39. Combination Sum Генерация комбинаций чисел, дающих целевую сумму [citations:2]. Элементы можно использовать неограниченно. 4 Medium 17. Letter Combinations of a Phone Number Must-have для мобильной разработки. Нужно сгенерировать все буквенные комбинации по цифрам на телефоне . 5 Medium 22. Generate Parentheses Генерация правильных скобочных последовательностей. Очень популярная задача на проверку понимания ограничений (условий остановки) в рекурсии . 6 Medium 79. Word Search Поиск слова в двумерной сетке (матрице) . Проверяет умение ходить в 4 стороны и откатывать состояние ("visited"). 7 Medium 90. Subsets II Тоже генерация подмножеств, НО с дубликатами . Проверяет, умеете ли вы пропускать повторяющиеся варианты. 8 Medium 77. Combinations Генерация всех возможных комбинаций длины k . Комбинации проще перестановок, так как порядок не важен. 🧠 Что в итоге? Этот набор задач покрывает все ключевые сценарии бэктрекинга:

Работа с индексами: Subsets, Combinations.

Работа с visited-массивом: Permutations, Word Search.

Суммирование/отсечения: Combination Sum, Generate Parentheses.

Мэппинг и строки: Letter Combinations.

Если вы уверенно решаете эти 8 задач, вы готовы к 90% вопросов по Backtracking на собеседовании в FAANG и других топовых компаниях .

Рекомендация: Обязательно начните с Subsets и Permutations. Понимание этих двух паттернов автоматически откроет вам решение остальных задач из списка.

Нужно разобрать алгоритм или код для какой-то из этих задач?

Расположи задачи в логической последовательности от более простых к более сложным, а также к каждой задаче дай минимальную теорию Отлично, давайте выстроим логическую последовательность изучения Backtracking. Я расположу задачи от самых простых ( введение в паттерн) к самым сложным (комбинации с ограничениями и обход матриц).

Также дам минимальную теорию к каждой — то, что нужно знать перед решением.

4. 77. Combinations (Medium) Почему здесь: Это производная от 78. Subsets, но мы ограничены размером k. Учимся контролировать глубину рекурсии.

Суть: Вернуть все сочетания из n по k (порядок не важен).

Техника: То же, что и 78, но остановка, когда subset.size() == k.

5. 90. Subsets II (Medium) 🔥 Продвинутые подмножества Почему здесь: Усложнение 78 — в массиве есть дубликаты. Нужно научиться пропускать повторы, чтобы в ответе не было [1,2] дважды.

Суть: Сгенерировать все уникальные подмножества (массив может содержать дубликаты).

Техника: Сортировка + в цикле if (i > start && nums[i] == nums[i-1]) continue;.

6. 39. Combination Sum (Medium) 🔥 Комбинации под сумму Почему здесь: Мы больше не просто собираем подмножества, а ищем сумму. Также важное отличие: один элемент можно использовать неограниченно.

Суть: Найти все уникальные комбинации чисел, дающие target.

Техника: Рекурсия с start (чтобы не было перестановок) и передачей остатка target - nums[i].

7. 46. Permutations (Medium) 🔥 Фундамент для перестановок Почему здесь: В отличие от сочетаний, здесь важен порядок ([1,2] и [2,1] — разные ответы). Нужен visited массив.

Суть: Вернуть все возможные перестановки (порядок важен).

Техника: Используем boolean[] used. В цикле перебираем все элементы, пропускаем уже used.

8. 17. Letter Combinations of a Phone Number (Medium) Почему здесь: Backtracking с маппингом. Задача показывает, как строить строки на основе данных из таблицы ( цифра -> буквы).

Суть: Сгенерировать все буквенные комбинации, которые соответствуют нажатию кнопок на телефоне.

Техника: Маппинг цифр в строки. Рекурсия по index строки с цифрами.

9. 22. Generate Parentheses (Medium) 🔥 Генерация скобок Почему здесь: Это задача на ограничения. Мы не можем поставить закрывающую скобку, если еще нет открывающей. Это учит отсекать заведомо неверные пути (pruning).

Суть: Сгенерировать все правильные скобочные последовательности длины 2 n.

Техника: Рекурсия с параметрами open и close. Добавляем '(', если open < n. Добавляем ')', если close < open.

10. 79. Word Search (Medium) 🔥 Поиск в матрице Почему здесь: Вершина бэктрекинга. Нужно управлять посещенными ячейками и ходить в 4 стороны. Сложность в обработке соседей и откате (убирании visited).

Суть: Проверить, существует ли слово в сетке (буквы должны быть соседними).

Техника: DFS по сетке. Пробуем начать с каждой ячейки. Красим board[i][j] = '#' (или visited[][]), чтобы не ходить по кругу.

Dynamic Programming

Level	Name	Link	Retention
Easy	509. Fibonacci Number	https://leetcode.com/problems/fibonacci-number/
Easy	70. Climbing Stairs	https://leetcode.com/problems/climbing-stairs/
Easy	746. Min Cost Climbing Stairs	https://leetcode.com/problems/min-cost-climbing-stairs/
Medium	322. Coin Change	https://leetcode.com/problems/coin-change/
Medium	198. House Robber	https://leetcode.com/problems/house-robber/
Medium	91. Decode Ways	https://leetcode.com/problems/decode-ways/
Medium	62. Unique Paths	https://leetcode.com/problems/unique-paths/
Medium	64. Minimum Path Sum	https://leetcode.com/problems/minimum-path-sum/
Medium	72. Edit Distance	https://leetcode.com/problems/edit-distance/

---

ID,URL,Title,Difficulty,Acceptance %,Frequency % 1,https://leetcode.com/problems/two-sum,Two Sum,Easy,57.1%,75.0% 2,https://leetcode.com/problems/add-two-numbers,Add Two Numbers,Medium,47.9%,50.0% 4,https://leetcode.com/problems/median-of-two-sorted-arrays,Median of Two Sorted Arrays,Hard,45.9%,50.0% 5,https://leetcode.com/problems/longest-palindromic-substring,Longest Palindromic Substring,Medium,37.3%,62.5% 7,https://leetcode.com/problems/reverse-integer,Reverse Integer,Medium,31.5%,37.5% 20,https://leetcode.com/problems/valid-parentheses,Valid Parentheses,Easy,43.7%,62.5% 21,https://leetcode.com/problems/merge-two-sorted-lists,Merge Two Sorted Lists,Easy,67.9%,62.5% 22,https://leetcode.com/problems/generate-parentheses,Generate Parentheses,Medium,78.2%,50.0% 23,https://leetcode.com/problems/merge-k-sorted-lists,Merge k Sorted Lists,Hard,58.8%,50.0% 33,https://leetcode.com/problems/search-in-rotated-sorted-array,Search in Rotated Sorted Array,Medium,44.1%,50.0% 56,https://leetcode.com/problems/merge-intervals,Merge Intervals,Medium,51.1%,75.0% 71,https://leetcode.com/problems/simplify-path,Simplify Path,Medium,50.0%,50.0% 76,https://leetcode.com/problems/minimum-window-substring,Minimum Window Substring,Hard,46.9%,50.0% 98,https://leetcode.com/problems/validate-binary-search-tree,Validate Binary Search Tree,Medium,35.3%,37.5% 101,https://leetcode.com/problems/symmetric-tree,Symmetric Tree,Easy,60.7%,50.0% 103,https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal,Binary Tree Zigzag Level Order Traversal,Medium,63.1%,37.5% 110,https://leetcode.com/problems/balanced-binary-tree,Balanced Binary Tree,Easy,57.8%,37.5% 124,https://leetcode.com/problems/binary-tree-maximum-path-sum,Binary Tree Maximum Path Sum,Hard,42.0%,50.0% 146,https://leetcode.com/problems/lru-cache,LRU Cache,Medium,46.8%,50.0% 150,https://leetcode.com/problems/evaluate-reverse-polish-notation,Evaluate Reverse Polish Notation,Medium,57.0%,25.0% 153,https://leetcode.com/problems/find-minimum-in-rotated-sorted-array,Find Minimum in Rotated Sorted Array,Medium,53.8%,37.5% 155,https://leetcode.com/problems/min-stack,Min Stack,Medium,57.7%,62.5% 161,https://leetcode.com/problems/one-edit-distance,One Edit Distance,Medium,34.5%,75.0% 199,https://leetcode.com/problems/binary-tree-right-side-view,Binary Tree Right Side View,Medium,69.5%,50.0% 200,https://leetcode.com/problems/number-of-islands,Number of Islands,Medium,63.8%,75.0% 205,https://leetcode.com/problems/isomorphic-strings,Isomorphic Strings,Easy,48.0%,75.0% 206,https://leetcode.com/problems/reverse-linked-list,Reverse Linked List,Easy,80.2%,37.5% 220,https://leetcode.com/problems/contains-duplicate-iii,Contains Duplicate III,Hard,24.4%,25.0% 228,https://leetcode.com/problems/summary-ranges,Summary Ranges,Easy,53.9%,87.5% 234,https://leetcode.com/problems/palindrome-linked-list,Palindrome Linked List,Easy,57.4%,25.0% 236,https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree,Lowest Common Ancestor of a Binary Tree,Medium,68.7%,50.0% 235,https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree,Lowest Common Ancestor of a Binary Search Tree,Medium,70.0%,37.5% 238,https://leetcode.com/problems/product-of-array-except-self,Product of Array Except Self,Medium,68.6%,50.0% 242,https://leetcode.com/problems/valid-anagram,Valid Anagram,Easy,67.8%,37.5% 986,https://leetcode.com/problems/interval-list-intersections,Interval List Intersections,Medium,72.9%,62.5% 279,https://leetcode.com/problems/perfect-squares,Perfect Squares,Medium,56.3%,50.0% 300,https://leetcode.com/problems/longest-increasing-subsequence,Longest Increasing Subsequence,Medium,59.0%,37.5% 2241,https://leetcode.com/problems/design-an-atm-machine,Design an ATM Machine,Medium,44.5%,62.5% 332,https://leetcode.com/problems/reconstruct-itinerary,Reconstruct Itinerary,Hard,44.3%,50.0% 340,https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters,Longest Substring with At Most K Distinct Characters,Medium,49.9%,50.0% 347,https://leetcode.com/problems/top-k-frequent-elements,Top K Frequent Elements,Medium,65.8%,25.0% 349,https://leetcode.com/problems/intersection-of-two-arrays,Intersection of Two Arrays,Easy,77.5%,37.5% 350,https://leetcode.com/problems/intersection-of-two-arrays-ii,Intersection of Two Arrays II,Easy,59.7%,37.5% 356,https://leetcode.com/problems/line-reflection,Line Reflection,Medium,36.3%,75.0% 362,https://leetcode.com/problems/design-hit-counter,Design Hit Counter,Medium,69.6%,50.0% 380,https://leetcode.com/problems/insert-delete-getrandom-o1,Insert Delete GetRandom O(1),Medium,55.3%,75.0% 387,https://leetcode.com/problems/first-unique-character-in-a-string,First Unique Character in a String,Easy,65.0%,37.5% 395,https://leetcode.com/problems/longest-substring-with-at-least-k-repeating-characters,Longest Substring with At Least K Repeating Characters,Medium,46.0%,25.0% 424,https://leetcode.com/problems/longest-repeating-character-replacement,Longest Repeating Character Replacement,Medium,59.0%,37.5% 438,https://leetcode.com/problems/find-all-anagrams-in-a-string,Find All Anagrams in a String,Medium,53.3%,75.0% 443,https://leetcode.com/problems/string-compression,String Compression,Medium,59.5%,87.5% 485,https://leetcode.com/problems/max-consecutive-ones,Max Consecutive Ones,Easy,64.6%,37.5% 487,https://leetcode.com/problems/max-consecutive-ones-ii,Max Consecutive Ones II,Medium,51.9%,25.0% 523,https://leetcode.com/problems/continuous-subarray-sum,Continuous Subarray Sum,Medium,31.2%,37.5% 1436,https://leetcode.com/problems/destination-city,Destination City,Easy,79.5%,37.5% 560,https://leetcode.com/problems/subarray-sum-equals-k,Subarray Sum Equals K,Medium,46.8%,75.0% 567,https://leetcode.com/problems/permutation-in-string,Permutation in String,Medium,48.4%,75.0% 605,https://leetcode.com/problems/can-place-flowers,Can Place Flowers,Easy,29.0%,37.5% 652,https://leetcode.com/problems/find-duplicate-subtrees,Find Duplicate Subtrees,Medium,60.6%,50.0% 658,https://leetcode.com/problems/find-k-closest-elements,Find K Closest Elements,Medium,49.4%,87.5% 680,https://leetcode.com/problems/valid-palindrome-ii,Valid Palindrome II,Easy,44.0%,75.0% 2627,https://leetcode.com/problems/debounce,Debounce,Medium,91.8%,37.5% 2657,https://leetcode.com/problems/find-the-prefix-common-array-of-two-arrays,Find the Prefix Common Array of Two Arrays,Medium,87.0%,75.0% 763,https://leetcode.com/problems/partition-labels,Partition Labels,Medium,81.8%,25.0% 771,https://leetcode.com/problems/jewels-and-stones,Jewels and Stones,Easy,89.5%,37.5% 849,https://leetcode.com/problems/maximize-distance-to-closest-person,Maximize Distance to Closest Person,Medium,49.6%,87.5% 896,https://leetcode.com/problems/monotonic-array,Monotonic Array,Easy,62.2%,50.0% 933,https://leetcode.com/problems/number-of-recent-calls,Number of Recent Calls,Easy,78.1%,50.0% 1868,https://leetcode.com/problems/product-of-two-run-length-encoded-arrays,Product of Two Run-Length Encoded Arrays,Medium,59.6%,37.5% 68,https://leetcode.com/problems/text-justification,Text Justification,Hard,50.4%,25.0% 674,https://leetcode.com/problems/longest-continuous-increasing-subsequence,Longest Continuous Increasing Subsequence,Easy,51.8%,37.5% 3105,https://leetcode.com/problems/longest-strictly-increasing-or-strictly-decreasing-subarray,Longest Strictly Increasing or Strictly Decreasing Subarray,Easy,64.9%,75.0% 938,https://leetcode.com/problems/range-sum-of-bst,Range Sum of BST,Easy,87.6%,37.5% 17,https://leetcode.com/problems/letter-combinations-of-a-phone-number,Letter Combinations of a Phone Number,Medium,65.5%,37.5% 227,https://leetcode.com/problems/basic-calculator-ii,Basic Calculator II,Medium,46.6%,50.0% 322,https://leetcode.com/problems/coin-change,Coin Change,Medium,47.9%,37.5% 2841,https://leetcode.com/problems/maximum-sum-of-almost-unique-subarray,Maximum Sum of Almost Unique Subarray,Medium,40.7%,25.0% 2743,https://leetcode.com/problems/count-substrings-without-repeating-character,Count Substrings Without Repeating Character,Medium,76.1%,50.0% 13,https://leetcode.com/problems/roman-to-integer,Roman to Integer,Easy,66.2%,25.0% 2570,https://leetcode.com/problems/merge-two-2d-arrays-by-summing-values,Merge Two 2D Arrays by Summing Values,Easy,81.8%,25.0% 470,https://leetcode.com/problems/implement-rand10-using-rand7,Implement Rand10() Using Rand7(),Medium,46.2%,25.0% 232,https://leetcode.com/problems/implement-queue-using-stacks,Implement Queue using Stacks,Easy,69.3%,37.5% 1656,https://leetcode.com/problems/design-an-ordered-stream,Design an Ordered Stream,Easy,82.6%,25.0% 881,https://leetcode.com/problems/boats-to-save-people,Boats to Save People,Medium,61.4%,25.0% 19,https://leetcode.com/problems/remove-nth-node-from-end-of-list,Remove Nth Node From End of List,Medium,51.0%,37.5% 739,https://leetcode.com/problems/daily-temperatures,Daily Temperatures,Medium,68.3%,37.5% 102,https://leetcode.com/problems/binary-tree-level-order-traversal,Binary Tree Level Order Traversal,Medium,72.2%,25.0% 295,https://leetcode.com/problems/find-median-from-data-stream,Find Median from Data Stream,Hard,54.2%,37.5% 415,https://leetcode.com/problems/add-strings,Add Strings,Easy,52.1%,37.5% 24,https://leetcode.com/problems/swap-nodes-in-pairs,Swap Nodes in Pairs,Medium,68.9%,25.0% 1650,https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree-iii,Lowest Common Ancestor of a Binary Tree III,Medium,82.9%,25.0% 53,https://leetcode.com/problems/maximum-subarray,Maximum Subarray,Medium,53.0%,37.5% 141,https://leetcode.com/problems/linked-list-cycle,Linked List Cycle,Easy,53.9%,25.0% 2667,https://leetcode.com/problems/create-hello-world-function,Create Hello World Function,Easy,82.0%,25.0% 1572,https://leetcode.com/problems/matrix-diagonal-sum,Matrix Diagonal Sum,Easy,84.1%,37.5% 1386,https://leetcode.com/problems/cinema-seat-allocation,Cinema Seat Allocation,Medium,43.6%,25.0% 239,https://leetcode.com/problems/sliding-window-maximum,Sliding Window Maximum,Hard,48.4%,25.0% 2665,https://leetcode.com/problems/counter-ii,Counter II,Easy,81.2%,25.0% 35,https://leetcode.com/problems/search-insert-position,Search Insert Position,Easy,50.7%,25.0% 2666,https://leetcode.com/problems/allow-one-function-call,Allow One Function Call,Easy,86.7%,37.5% 1496,https://leetcode.com/problems/path-crossing,Path Crossing,Easy,62.6%,37.5% 994,https://leetcode.com/problems/rotting-oranges,Rotting Oranges,Medium,58.1%,25.0% 181,https://leetcode.com/problems/employees-earning-more-than-their-managers,Employees Earning More Than Their Managers,Easy,72.8%,25.0% 2215,https://leetcode.com/problems/find-the-difference-of-two-arrays,Find the Difference of Two Arrays,Easy,81.3%,25.0% 2043,https://leetcode.com/problems/simple-bank-system,Simple Bank System,Medium,69.8%,25.0% 2956,https://leetcode.com/problems/find-common-elements-between-two-arrays,Find Common Elements Between Two Arrays,Easy,84.4%,25.0% 341,https://leetcode.com/problems/flatten-nested-list-iterator,Flatten Nested List Iterator,Medium,65.6%,25.0% 974,https://leetcode.com/problems/subarray-sums-divisible-by-k,Subarray Sums Divisible by K,Medium,56.0%,25.0% 2629,https://leetcode.com/problems/function-composition,Function Composition,Easy,86.9%,37.5% 9,https://leetcode.com/problems/palindrome-number,Palindrome Number,Easy,60.2%,25.0% 74,https://leetcode.com/problems/search-a-2d-matrix,Search a 2D Matrix,Medium,53.5%,25.0% 2006,https://leetcode.com/problems/count-number-of-pairs-with-absolute-difference-k,Count Number of Pairs With Absolute Difference K,Easy,85.3%,25.0% 1438,https://leetcode.com/problems/longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit,Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit,Medium,57.3%,25.0%

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Недостающие задачи (есть в итоговом списке, нет в вашем) Тема ID недостающих задач Hash Map 146, 205, 349, 350, 380, 387, 652, 771, 1436 Binary Search 4, 33 Two Pointers 680 Sliding Window 340, 395, 485, 487 Prefix Sum 523 Intervals 986 Stack, Queue 227, 341, 739, 933 Linked List 23, 24 Binary Tree (DFS) 110, 124, 235 Binary Tree (BFS) 103 BST 98, 110, 235 Backtracking 17, 22 Примечания

110. Balanced Binary Tree — относится и к DFS, и к BST (попала в две темы)

111. Lowest Common Ancestor of a BST — относится и к DFS, и к BST

Задачи 4, 33, 124, 146, 220, 239, 295, 322, 332, 340, 341, 347, 356, 362, 395, 424, 438, 443, 487, 523, 560, 567, 605, 652, 658, 763, 849, 881, 938, 986, 1438, 1868, 2241, 2657, 2743, 2841, 3105 — есть в итоговом списке, но отсутствуют в вашем и не вошли в таблицу выше, так как их тема не совпала с вашими 12 категориями.

Хорошо, тогда задачи, которые не вошли в список разбей также по темам, которых у меня нет Задачи из итогового списка, которые не вошли в ваши 12 тем — разбивка по новым темам

1. Dynamic Programming (DP) ID Название Уровень Частота 5 Longest Palindromic Substring Medium 62.5% 53 Maximum Subarray Medium 37.5% 300 Longest Increasing Subsequence Medium 37.5% 322 Coin Change Medium 37.5% 124 Binary Tree Maximum Path Sum Hard 50% 279 Perfect Squares Medium 50%

2. Graph / Matrix Traversal (BFS/DFS на графах) ID Название Уровень Частота 200 Number of Islands Medium 75% 994 Rotting Oranges Medium 25% 332 Reconstruct Itinerary Hard 50% 1572 Matrix Diagonal Sum Easy 25% 1650 Lowest Common Ancestor III Medium 25%

3. Heap / Priority Queue ID Название Уровень Частота 23 Merge k Sorted Lists Hard 50% 347 Top K Frequent Elements Medium 25% 295 Find Median from Data Stream Hard 37.5% 658 Find K Closest Elements Medium 87.5%

4. Design / OOP ID Название Уровень Частота 146 LRU Cache Medium 50% 341 Flatten Nested List Iterator Medium 25% 380 Insert Delete GetRandom O(1) Medium 75% 362 Design Hit Counter Medium 50% 1656 Design an Ordered Stream Easy 25% 2043 Simple Bank System Medium 25% 2241 Design an ATM Machine Medium 62.5%

5. Bit Manipulation ID Название Уровень Частота

6. Math / Geometry ID Название Уровень Частота 7 Reverse Integer Medium 37.5% 9 Palindrome Number Easy 25% 13 Roman to Integer Easy 25% 415 Add Strings Easy 37.5% 470 Implement Rand10() Medium 25% 356 Line Reflection Medium 75%

7. Greedy ID Название Уровень Частота 605 Can Place Flowers Easy 37.5% 849 Maximize Distance to Closest Person Medium 87.5% 881 Boats to Save People Medium 25%

8. String / Array (простые манипуляции) ID Название Уровень Частота 161 One Edit Distance Medium 75% 228 Summary Ranges Easy 87.5% 443 String Compression Medium 87.5% 896 Monotonic Array Easy 50% 1436 Destination City Easy 37.5% 1496 Path Crossing Easy 37.5% 2215 Find the Difference of Two Arrays Easy 25% 2570 Merge Two 2D Arrays by Summing Values Easy 25% 2657 Find the Prefix Common Array Medium 75% 2743 Count Substrings Without Repeating Medium 50% 2956 Find Common Elements Between Two Arrays Easy 25% 3105 Longest Increasing/Decreasing Subarray Easy 75%

9. Union Find / Disjoint Set ID Название Уровень Частота 200 Number of Islands Medium 75% Можно решать и через DFS, и через Union Find.

10. Two Pointers (дополнительные — уже есть в вашей теме, но не вошли) ID Название Уровень Частота 680 Valid Palindrome II Easy 75%

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Тема ID задач Array 4, 33, 35, 53, 56, 74, 153, 200, 228, 238, 300, 322, 349, 350, 380, 485, 560, 605, 674, 849, 881, 896, 1868, 2215, 2570, 2956, 2006 Hash Table 205, 242, 349, 350, 380, 387, 438, 523, 560, 652, 771, 1436, 1656, 2043, 2215, 2657, 2956, 2006 String 5, 13, 17, 20, 22, 49, 68, 71, 76, 161, 205, 227, 242, 332, 340, 387, 395, 415, 424, 438, 443, 567, 680, 771 Sliding Window 76, 340, 395, 424, 438, 485, 487, 567, 1438, 2743, 2841 Two Pointers 19, 141, 234, 443, 567, 680, 881, 986 Binary Search 33, 35, 74, 153, 220, 300, 349, 350, 658 Linked List 2, 19, 21, 23, 24, 141, 146, 206, 234 Tree / DFS / BFS 98, 101, 102, 103, 110, 124, 199, 235, 236, 652, 938, 994, 1650 Stack / Queue 20, 22, 71, 146, 150, 155, 227, 232, 239, 341, 739, 933 Heap / Priority Queue 23, 239, 295, 347, 658 Math 7, 9, 13, 415, 470 Backtracking 17, 22 Dynamic Programming 53, 279, 300, 322, 674 Design 146, 155, 232, 341, 362, 380, 933, 1656, 2043, 2241, 2627, 2629, 2665, 2666, 2667 Sorting 56, 242, 347, 349, 350 Matrix 74, 1572 SQL 181