Solve problems from Leetcode. All the codes are tested using online-judge.

Here is a difficulty and frequency distribution chart for each problem (which I got from the Internet and is very useful).

• Edit Distance
• Maximum Subarray
• Minimum Path Sum
• Unique Paths
• Unique Paths II
• Longest Palindromic Substring
• Interleaving String
• Triangle
• Distinct Subsequences
• Decode Ways
• Palindrome Partitioning II
• Maximal Rectangle

• N-Queens
• N-Queens II
• Balanced Binary Tree
• Binary Tree Inorder Traversal
• Binary Tree Maximum Path Sum
• Convert Sorted Array to Binary Search Tree
• Convert Sorted List to Binary Search Tree
• Flatten Binary Tree to Linked List
• Maximum Depth of Binary Tree
• Minimum Depth of Binary Tree
• Path Sum
• Permutations
• Permutations II
• Populating Next Right Pointers in Each Node
• Pow(x, n)
• Same Tree
• Subsets
• Sum Root to Leaf Numbers
• Swap Nodes in Pairs
• Symmetric Tree
• Valid Palindrome
• Validate Binary Search Tree
• Restore IP Addresses
• Combinations
• Interleaving String (dp is the best)
• Combination Sum II
• Letter Combinations of a Phone Numbers
• Word Search
• Construct Binary Tree from Inorder and Postorder Traversal
• Construct Binary Tree from Preorder and Inorder Traversal
• Generate Parentheses
• Surrounded Regions (runtime error)
• Palindrome Partitioning
• Combination Sum
• Sudoku Solver
• Unique Binary Search Trees II

• Search Insert Position
• Search a 2D Matrix
• Search for a Range
• Search in Rotated Sorted Array
• Sqrt(x)

• Container With Most Water
• Count and Say
• First Missing Positive
• Implement strStr()
• Jump Game
• Jump Game II
• Length of Last Word
• Longest Common Prefix
• Longest Substring Without Repeating Characters
• Merge Sorted Array
• Palindrome Number
• Plus One
• Remove Duplicates from Sorted Array
• Remove Duplicates from Sorted Array II
• Remove Element
• Reverse Integer
• Search in Rotated Sorted Array II
• Sort Colors
• Two Sum
• 3Sum
• 3Sum Closest
• 4Sum
• Add Binary
• Longest Palindromic Substring
• Next Permutation
• Longest Valid Parentheses
• Climbing Stairs
• Permutation Sequence
• Simplify Path
• String to Integer (atoi)
• Minimum Window Substring
• Longest Consecutive Sequence
• Trapping Rain Water
• Valid Number

• Add Two Numbers
• Convert Sorted List to Binary Search Tree
• Merge Two Sorted Lists
• Partition List
• Remove Duplicates from Sorted List
• Remove Duplicates from Sorted List II
• Remove Nth Node From End of List
• Reverse Linked List II
• Reverse Nodes in k-Group
• Rotate List
• Swap Nodes in Pairs

• Binary Tree Inorder Traversal
• Binary Tree Level Order Traversal II
• Valid Parentheses

• Binary Tree Level Order Traversal
• Binary Tree Level Order Traversal II
• Populating Next Right Pointers in Each Node II
• Symmetric Tree
• Surrounded Regions
• Word Ladder

• Balanced Binary Tree
• Binary Tree Inorder Traversal
• Binary Tree Level Order Traversal
• Binary Tree Level Order Traversal II
• Binary Tree Maximum Path Sum
• Convert Sorted Array to Binary Search Tree
• Convert Sorted List to Binary Search Tree
• Flatten Binary Tree to Linked List
• Maximum Depth of Binary Tree
• Minimum Depth of Binary Tree
• Path Sum
• Same Tree
• Sum Root to Leaf Numbers
• Symmetric Tree
• Validate Binary Search Tree