Talk is cheap, show me the code ~ This part mostly record my problem-solving idea, coding and summary of leetcode algorithm problems. Note: all solutions are based on Python

ID Title Difficulty Solution
1 Two Sum Easy HashMap
15 Three Sum Medium Array
18 Four Sum Medium Array
20 Valid Parentheses Easy Stack
22 Generate Parentheses Medium Recursion
24 Swap Nodes in Pairs Medium LinkedList
25 Reverse Nodes in k-Group Hard LinkedList
36 Valid Sudoku Medium Prune
37 Sudoku Solver Hard Prune
50 Pow(x, n) Medium Recursion
51 N-Queens Hard Prune
52 N-Queens II Hard Prune
98 Validate Binary Search Tree Medium Tree
102 Binary Tree Level Order Traversal Medium Tree
104 Maximum Depth of Binary Tree Easy Tree
111 Minimum Depth of Binary Tree Easy Tree
122 Best Time to Buy and Sell Stock II Easy Greedy
141 Linked List Cycle Easy LinkedList
142 Linked List Cycle II Medium LinkedList
169 Majority Element Easy Sort
206 Reverse Linked List Medium LinkedList
225 Implement Stack using Queues Easy Queue
232 Implement Queue using Stacks Easy Stack
235 Lowest Common Ancestor of a Binary Search Tree Easy Tree
236 Lowest Common Ancestor of a Binary Tree Medium Tree
239 Sliding Window Maximum Hard Queue
242 Valid Anagram Easy HashMap
703 Kth Largest Element in a Stream Medium Stack