14 Patterns to Ace Any Coding Interview Question

14 Patterns to Ace Any Coding Interview Question

1. Sliding Window

• Maximum sum subarray of size ‘K’ (easy)
• Longest substring with ‘K’ distinct characters (medium)
• String anagrams (hard)

2. Two Pointers or Iterators

• Squaring a sorted array (easy)
• Triplets that sum to zero (medium)
• Comparing strings that contain backspaces (medium)

3. Fast and Slow Pointers

• Linked List Cycle (easy)
• Palindrome Linked List (medium)
• Cycle in a Circular Array (hard)

4. Merge Intervals

• Intervals Intersection (medium)
• Maximum CPU Load (hard)

5. Cyclic sort

• Find the Missing Number (easy)
• Find the Smallest Missing Positive Number (medium)

6. In-place reversal of linked list

• Reverse a sub list (medium)
• Reverse every K-element sub-list (medium)
  • Recursive
  • Iterative

7. Tree BFS, use a queue

Use a queue

• Binary Tree Level Order Traversal (easy)
  • Recursive
  • Iterative
• Zigzag Traversal (medium)
• Minimum Depth of Binary Tree (Easy)
• Average of Levels in Binary Tree (Easy)
• Cousins in Binary Tree (Easy)
• Binary Tree Level Order Traversal II (Medium)
• Binary Tree Vertical Order Traversal (Medium)
• N-ary Tree Level Order Traversal (Medium)

8. Tree DFS, use a stack

• Sum of Path Numbers (medium)

  • recursive
  • Iterative

• All Paths for a Sum (medium)

  • recursive
  • Iterative

9. 2 Heaps

• Find the Median of a Number Stream (medium)

10. Subsets

• Subsets With Duplicates (easy)
• String Permutations by changing case (medium)

11. Modify Binary Search

• Binary Search
• Infinite Array (medium)
• Search in a Sorted Array of Unknown Size

12. Top K elements

• Top ‘K’ Frequent Numbers (medium)
• Kth Largest Element in an Array
• K Closest Points to Origin

13: k ways merge

• Merge K Sorted Lists
• smallest sum k pair
• kth-smallest-element-in-a-sorted-matrix/

14: Topological sort

• Minimum height of a tree (hard): https://leetcode.com/problems/minimum-height-trees/
• Course Schedule: https://leetcode.com/problems/course-schedule/

Learn and solve tree traversal

• Learn recursive solutions first
• Learn iterative solution later

Acknowledgements

• HackerNoon, 14 Patterns to Ace Any Coding Interview Question