参考：http://blog.csdn.net/yutianzuijin/article/details/11477603/
ID | 问题 | 频率 | 数据结构 | 算法 | 1Two Sum5array、setsort、Two Pointers8String to Integer (atoi)5stringMath153Sum5arrayTwo Pointers20Valid Parentheses5stringStack21Merge Two Sorted Lists5linked listsort、Two Pointers、merge28Implement strStr()5stringTwo Pointers、KMP、rolling hash50Pow(x, n)5 Binary Search、Math56Merge Intervals5array、linked list、red-black treesort、merge57Insert Interval5arraysort65Valid Number5stringMath70Climbing Stairs5 DP73Set Matrix Zeroes5array 88Merge Sorted Array5arrayTwo Pointers、merge98Validate Binary Search Tree5treeDFS125Valid Palindrome5stringTwo Pointers127Word Ladder5graphBFS、path2Add Two Numbers4linked listTwo Pointers、Math12Integer to Roman4 Math13Roman to Integer4 Math22Generate Parentheses4stringDFS23Merge k Sorted Lists4linked list、heapsort、Two Pointersmerge24Swap Nodes in Pairs4linked list 27Remove Element4arrayTwo Pointers46Permutations4arraypermutation49Anagrams4string、hashtable 67Add Binary4stringTwo Pointers、Math69Sqrt(x)4 Binary Search77Combinations4 combination78Subsets4arrayRecursion、combination79Word Search4arrayDFS91Decode Ways4stringRecursion、DP102Binary Tree Level Order Traversal4treeBFS129Sum Root to Leaf Numbers4treeDFS131Palindrome Partitioning4stringDFS4Median of Two Sorted Arrays3arrayBinary Search7Reverse Integer3 Math10Regular Expression Matching3stringRecursion、DP17Letter Combinations of a Phone Number3stringDFS19Remove Nth Node From End of List3linked listTwo Pointers26Remove Duplicates from Sorted Array3arrayTwo Pointers29Divide Two Integers3 Binary Search33Search in Rotated Sorted Array3arrayBinary Search34Search for a Range3arrayBinary Search39Combination Sum3arraycombination43Multiply Strings3stringTwo Pointers、Math44Wildcard Matching3stringRecursion、DP、greedy51N-Queens3arrayDFS52N-Queens II3arrayDFS53Maximum Subarray3arrayDP62Unique Paths3arrayDP63Unique Paths II3arrayDP64Minimum Path Sum3arrayDP72Edit Distance3stringDP74Search a 2D Matrix3arrayBinary Search81Search in Rotated Sorted Array II3arrayBinary Search82Remove Duplicates from Sorted List II3linked listRecursion、Two Pointers83Remove Duplicates from Sorted List3linked list 86Partition List3linked listTwo Pointers93Restore IP Addresses3stringDFS94Binary Tree Inorder Traversal3tree、hashtableRecursion、morris、Stack103Binary Tree Zigzag Level Order Traversal3queue、treeBFS、Stack105Construct Binary Tree from Preorder and Inorder Tr3array、treeDFS106Construct Binary Tree from Inorder and Postorder T3array、treeDFS108Convert Sorted Array to Binary Search Tree3treeDFS109Convert Sorted List to Binary Search Tree3linked listRecursion、Two Pointers112Path Sum3treeDFS114Flatten Binary Tree to Linked List3treeRecursion、Stack116Populating Next Right Pointers in Each Node3treeDFS128Longest Consecutive Sequence3array 130Surrounded Regions3arrayBFS、DFS132Palindrome Partitioning II3stringDP3Longest Substring Without Repeating Characters2string、hashtableTwo Pointers5Longest Palindromic Substring2string 9Palindrome Number2 Math11Container With Most Water2arrayTwo Pointers184Sum2array 25Reverse Nodes in k-Group2linked listRecursion、Two Pointers31Next Permutation2arraypermutation35Search Insert Position2array 36Valid Sudoku2array 37Sudoku Solver2arrayDFS38Count and Say2stringTwo Pointers40Combination Sum II2arraycombination41First Missing Positive2arraysort42Trapping Rain Water2arrayTwo Pointers、Stack45Jump Game II2array 47Permutations II2arraypermutation48Rotate Image2array 54Spiral Matrix2array 55Jump Game2array 59Spiral Matrix II2array 61Rotate List2linked listTwo Pointers66Plus One2arrayMath68Text Justification2string 75Sort Colors2arraysort、Two Pointers76Minimum Window Substring2stringTwo Pointers80Remove Duplicates from Sorted Array II2arrayTwo Pointers84Largest Rectangle in Histogram2arrayStack87Scramble String2stringRecursion、DP89Gray Code2 combination90Subsets II2arrayRecursion、combination92Reverse Linked List II2linked listTwo Pointers97Interleaving String2stringRecursion、DP99Recover Binary Search Tree2treeDFS101Symmetric Tree2treeDFS110Balanced Binary Tree2treeDFS113Path Sum II2treeDFS115Distinct Subsequences2stringDP117Populating Next Right Pointers in Each Node II2treeDFS124Binary Tree Maximum Path Sum2treeDFS6ZigZag Conversion1string 14Longest Common Prefix1string 163Sum Closest1arrayTwo Pointers30Substring with Concatenation of All Words1stringTwo Pointers32Longest Valid Parentheses1stringDP58Length of Last Word1string 60Permutation Sequence1 permutation、Math71Simplify Path1stringStack85Maximal Rectangle1arrayDP、Stack95Unique Binary Search Trees II1treeDP、DFS96Unique Binary Search Trees1treeDP100Same Tree1treeDFS104Maximum Depth of Binary Tree1treeDFS107Binary Tree Level Order Traversal II1treeBFS111Minimum Depth of Binary Tree1treeDFS118Pascal’s Triangle1array 119Pascal’s Triangle II1array 120Triangle1arrayDP121Best Time to Buy and Sell Stock1arrayDP122Best Time to Buy and Sell Stock II1arraygreedy123Best Time to Buy and Sell Stock III1arrayDP126Word Ladder II1 
