Algorithm Playground

This is a Java Language edition, and Python edition also available algorithmPlayground_python.

We use junit as the project unit test framework, as for the maven project structure, so you can run all test case by execute shell command mvn test -B

Algorithm & Data Structure problem / solution sets

Array

• Container With Most Water
• Trapping Rain Water
• Maximum Swap
• Sort Colors
• Move Zeroes
• Remove Duplicates from Sorted Array
• Russian Doll Envelopes
• Merge Intervals

Linked List

• Reverse Linked List
• Swap Nodes in Pairs
• Linked List Cycle
• Linked List Cycle II
• Remove Nth Node From End of List
• Reverse Nodes in k-Group
• Middle of the Linked List
• Merge Two Sorted Lists
• Merge k Sorted Lists
• Add Two Numbers
• Add Two Numbers II
• Reorder List
• Remove Duplicates from Sorted List
• Remove Duplicates from Sorted List II

Stack & Queue

• Valid Parentheses
• Implement Stack using Queues
• Implement Queue using Stacks

deque

• Sliding Window Maximum

Skip-list

HashMap & Set

• Valid Anagram

• Two Sum

• 3Sum

• 4Sum

• Two Sum II - Input array is sorted

• Majority Element

Tree - Binary Search Tree

• Validate Binary Search Tree
• Lowest Common Ancestor of a Binary Search Tree
• Lowest Common Ancestor of a Binary Tree
• Binary Tree Inorder Traversal
• Binary Tree Preorder Traversal
• Binary Tree Postorder Traversal

Priority Queue(heap)

• Sliding Window Maximum
• Kth Largest Element in a Stream
• Kth Largest Element in an Array
• Find Median from Data Stream
• Sliding Window Median
• Top K Frequent Elements

possible

lexicographical

• Lexicographical Numbers
• K-th Smallest in Lexicographical Order

Binary Search

• Pow(x, n)
• Sqrt(x)
• Divide Two Integers
• Search in Rotated Sorted Array
• Russian Doll Envelopes

Breadth First Search

• Binary Tree Level Order Traversal
• Maximum Depth of Binary Tree
• Minimum Depth of Binary Tree
• Binary Tree Right Side View

Depth First Search

• Binary Tree Level Order Traversal
• Maximum Depth of Binary Tree
• Minimum Depth of Binary Tree
• Generate Parentheses
• Number of Islands
• Binary Tree Right Side View

Basic algorithm thinking

Recursion

• Pow(x, n)
• Generate Parentheses

Divide & Conquer

• Pow(x, n)
• Majority Element
• Maximum Depth of Binary Tree
• Minimum Depth of Binary Tree

Greedy

• Candy
• Divide Chocolate

Backtracking

• Combinations
• Restore IP Addresses
• Regular Expression Matching
• Word Search
• Generate Parentheses
• Letter Combinations of a Phone Number
• Combination Sum
• Combination Sum II
• Subsets
• Subsets II
• Android Unlock Patterns
• Permutations
• Permutations II

Dynamic Programming

• Fibonacci Number
• Climbing Stairs
• Edit Distance
• Triangle
• Maximum Product Subarray
• Best Time to Buy and Sell Stock
• Best Time to Buy and Sell Stock II
• Best Time to Buy and Sell Stock III
• Best Time to Buy and Sell Stock IV
• Best Time to Buy and Sell Stock with Cooldown
• Best Time to Buy and Sell Stock with Transaction Fee
• Longest Increasing Subsequence
• Russian Doll Envelopes
• Coin Change
• Maximum Subarray
• Trapping Rain Water
• Super Egg Drop
• Android Unlock Patterns
• House Robber
• House Robber II
• House Robber III
• Factorial of a number - NOT a LeetCode problem

Advanced data structure & algorithm

trie Tree

• Implement Trie (Prefix Tree)

Union-find

• Number of Islands
• Friend Circles

Bitmap

Bloom-filter

Bitwise

• Number of 1 Bits
• Power of Two
• Counting Bits
• UTF-8 Validation

String

• Implement strStr()

System design Problem / Solution sets

Basic components

cache

LRU Cache

• LRU Cache

Design Twitter (news feed system)

the full system design solution could be found in this blog(Mandarin) 如何设计一个精简版的微博（或者Twitter）？
and part of the code design problem:

• Design Twitter

Design TinyURL

The solution could be found in this blog(Mandarin)如何设计一个短网址服务 and part of the code design problem:

Encode and Decode TinyURL

• Encode and Decode TinyURL