Top 10 Algorithms for Coding Interview

1. String/Array/Matrix

Rotate Array Reverse Words in a String Evaluate Reverse Polish Notation (Stack) Isomorphic Strings Word Ladder (BFS) Word Ladder II (BFS) Median of Two Sorted Arrays Kth Largest Element in an Array Wildcard Matching Regular Expression Matching Merge Intervals Insert Interval Two Sum Two Sum II Two Sum III 3Sum 4Sum 3Sum Closest String to Integer Merge Sorted Array Valid Parentheses Longest Valid Parentheses Implement strStr() Minimum Size Subarray Sum Search Insert Position Longest Consecutive Sequence Valid Palindrome ZigZag Conversion Add Binary Length of Last Word Triangle Contains Duplicate: I, II, III Remove Duplicates from Sorted Array: I, II Remove Element Move Zeroes Longest Substring Without Repeating Characters Longest Substring that contains 2 unique characters [Google] Substring with Concatenation of All Words Minimum Window Substring Find Minimum in Rotated Sorted Array: I, II Search in Rotated Array: I, II Min Stack Majority Element: I, II Bulls and Cows Largest Rectangle in Histogram Longest Common Prefix [Google] Largest Number Simplify Path Compare Version Numbers Gas Station Pascal's Triangle: I, II Container With Most Water Candy [Google] Trapping Rain Water Count and Say Search for a Range Basic Calculator, Basic Calculator II Group Anagrams Shortest Palindrome Rectangle Area Summary Ranges Increasing Triplet Subsequence Get Target Using Number List And Arithmetic Operations Reverse Vowels of a String Flip Game, Flip Game II Missing Number, Find the duplicate number, First Missing Positive Valid Anagram, Group Shifted Strings Top K Frequent Elements Find Peak Element Word Pattern, Word Pattern II H-Index, H-Index II Palindrome Pairs One Edit Distance Scramble String First Bad Version Integer to English Words Text Justification Remove Invalid Parentheses Intersection of Two Arrays, Intersection of Two Arrays II Sliding Window Maximum, Moving Average from Data Stream Guess Number Higher or Lower

2. Matrix

Set Matrix Zeroes Spiral Matrix Spiral Matrix II Search a 2D Matrix Search a 2D Matrix II Rotate Image [Palantir] Valid Sudoku Minimum Path Sum (DP) [Google] Unique Paths (DP) [Google] Unique Paths II (DP) Number of Islands (DFS/BFS) Number of Islands II (Disjoint Set) Number of Connected Components in an Undirected Graph Surrounded Regions (BFS) Maximal Rectangle Maximal Square Word Search (DFS) Word Search II Range Sum Query 2D – Immutable Longest Increasing Path in a Matrix (DFS) Shortest Distance from All Buildings Game of Life Paint House, Paint House II Sudoku Solver (DFS) Walls and Gates (DFS/BFS) Tic-Tac-Toe Best Meeting Point

3. Linked List

Implement a Stack Using an Array Add Two Numbers Reorder List Linked List Cycle Copy List with Random Pointer Merge Two Sorted Lists Odd Even Linked List Remove Duplicates from Sorted List Remove Duplicates from Sorted List II Partition List LRU Cache Intersection of Two Linked Lists Remove Linked List Elements Swap Nodes in Pairs Reverse Linked List, Reverse Linked List II Print Linked List in Reversed Order Remove Nth Node From End of List (Fast-Slow Pointers) Implement Stack using Queues Implement Queue using Stacks Palindrome Linked List Implement a Queue using an Array Delete Node in a Linked List Reverse Nodes in k-Group

4. Tree, Heap and Trie

Binary Tree Traversal: Preorder, Inorder, Postorder, Level Order Level Order II Vertical Order Invert Binary Tree Kth Smallest Element in a BST Binary Tree Longest Consecutive Sequence Validate Binary Search Tree Flatten Binary Tree to Linked List Path Sum (DFS or BFS) Path Sum II (DFS) Construct Binary Tree from Inorder and Postorder Traversal Construct Binary Tree from Preorder and Inorder Traversal Convert Sorted Array to Binary Search Tree [Google] Convert Sorted List to Binary Search Tree [Google] Minimum Depth of Binary Tree Binary Tree Maximum Path Sum Balanced Binary Tree Symmetric Tree Binary Search Tree Iterator Binary Tree Right Side View Lowest Common Ancestor of a Binary Search Tree Lowest Common Ancestor of a Binary Tree Verify Preorder Serialization of a Binary Tree Populating Next Right Pointers in Each Node Populating Next Right Pointers in Each Node II Unique Binary Search Trees (DP) Unique Binary Search Trees II (DFS) Sum Root to Leaf Numbers (DFS) Count Complete Tree Nodes Closest Binary Search Tree Value Binary Tree Paths Maximum Depth of Binary Tree Recover Binary Search Tree Same Tree Serialize and Deserialize Binary Tree Inorder Successor in BST Find Leaves of Binary Tree Largest BST Subtree

Heap

Merge k sorted arrays [Google] Merge k Sorted Lists Find Median from Data Stream Meeting Rooms II, Meeting Rooms Range Addition

Trie

Implement Trie (Prefix Tree) Add and Search Word – Data structure design (DFS)

Segment Tree

Range Sum Query – Mutable The Skyline Problem

5. Graph

Clone Graph Course Schedule, Course Schedule II Minimum Height Trees Reconstruct Itinerary Graph Valid Tree

6. Sorting

Bubble Sort Selection Sort Insertion Sort Merge Sort Quick Sort Heap Sort Counting Sort Radix Sort Bucket Sort Merge Overlapping Intervals Form the Largest Number Sort array of 0s, 1s, and 2s K'th Smallest/Largest Minimum Platforms Required Case-specific Sorting of Strings Sort by Frequency Minimum Operations for Distinct

7. Dynamic Programming

Edit Distance Longest Common Subsequence Knapsack Problem Matrix Chain Multiplication Coin Change Maximum Subarray Longest Increasing Subsequence Word Break House Robber Jump Game Best Time to Buy and Sell Stock Decode Ways Palindrome Partitioning

8. Bit Manipulation

Single Number Reverse Bits Number of 1 Bits Maximum Binary Gap Sum of Two Integers Missing Number Counting Bits Bitwise AND of Numbers Range Gray Code Maximum Product of Word Lengths

9. Combinations and Permutations

Permutations Permutations II Permutation Sequence Generate Parentheses Combination Sum Combinations Letter Combinations of a Phone Number Restore IP Addresses Factor Combinations

10. Math

Reverse Integer Palindrome Number Pow(x, n), Power of Two, Power of Three, Power of Four Subsets Fraction to Recurring Decimal [Google] Excel Sheet Column Number Excel Sheet Column Title Factorial Trailing Zeroes Happy Number Count Primes Plus One Divide Two Integers Multiply Strings Max Points on a Line Product of Array Except Self Integer Break Add Digits Ugly Number, Ugly Number II, Super Ugly Number Find K Pairs with Smallest Sums