JiaqiLiu / LeetCode-Summary

My personal summary of LeetCode problems, including solution optimization methods and some thoughts on it.

LeetCode-Summary

General Methods & Tips

1. Binary Search Coding Principles
2. XOR Swapping Method
3. GCD

Catalog

Array

1. k Sum
   2 Sum--exactly one solution/no duplicates

   • HashMap:O(n) <=no duplicate
   • Sort+Two Pointers:O(nlogn); if sorted:O(n)

   3 Sum-contains duplicates

   • Sort+Two Pointers:O(n^2)

   3 Sum Closest

   • Sort+Two Pointers:O(n^2), cannot use hashmap since it looks for the closest answer instead of the exact one.

   4 Sum

   • Sort+Two Pointers:O(n^3),some modifications to avoid useless computations
   • 'Two Sum' solution:O(n^2*logn)

2. Rotation   -to be continued
   Rotate Array
   
   

3. Pascal's Triangle II
   
   

4. Contains Duplicate -not finnished yet
   Contains Duplicate I
   Contains Duplicate II
   
   

5. Intersection of Two Arrays -to be continued
   Intersection of Two Arrays I
   

String

1. String

Math

1. Math Solutions
   Gray Code
   Rotate Function
   
   

LinkedList

1. Fast & Slow Pointers
   Rotate List
   
   

Dynamic Programming

1. Best Time to Buy and Sell Stock -to be continued
   Best Time to Buy and Sell Stock
   Best Time to Buy and Sell Stock II
   Best Time to Buy and Sell Stock with Cooldown
   
2. Majority Element
   
3. Dynamic Programming - 2D -to be continued
   Minimum Path Sum

Binary Search

1. Find Peak Element -to be continued

Heap

1. Heap
   K-th Smallest Element in a Sorted Matrix
   Find K Pairs with Smallest Sums

Backtracking

1. Classic Backtrackings
   Palindrome Partitioning
   Combinations
   Combination Sum
   Combination Sum II
   Combination Sum III
   Permutation
   Permutation II
   Subsets
   Subsets II

2. Backtracking
   Generate Parentheses
   Letter Combinations of a Phone Number
   Binary Watch
   Word Search

Tree

1. Tree Traversal
   Binary Tree Preorder Traversal
   Binary Tree Inorder Traversal
   Binary Tree Postorder Traversal
   Binary Tree Level Order Traversal
   Binary Tree Zigzag Level Order Traversal