记忆力不好的博客

34. Search for a Range Given a sorted array of integers, find the starting and ending position of a given target value. Your algorithm's runtime complexity must be in the order of O(log n).

Longest Palindromic Substring Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substri

59. Spiral Matrix II Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example, Given n = 3, You should return the following matrix: [ [ 1

41. First Missing Positive Given an unsorted integer array, find the first missing positive integer. For example, Given [1,2,0] return 3, and [3,4,-1,1] return 2. Your algorithm should ru

287. Find the Duplicate Number Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that th

The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return all distinct solutions to the n-queens puzzle.

300. Longest Increasing Subsequence Given an unsorted array of integers, find the length of longest increasing subsequence. For example, Given [10, 9, 2, 5, 3, 7, 101, 18], The longest incre

Given an integer (signed 32 bits), write a function to check whether it is a power of 4. Example: Given num = 16, return true. Given num = 5, return false. Follow up: Could you solve it without

46.Permutations Total Accepted: 96713 Total Submissions: 271529 Difficulty: Medium Given a collection of distinct numbers, return all possible permutations.For example, [1,2,3] have the following pe

50. Pow(x, n) Implement pow(x, n). 这道题求x的n次幂，用二分法，时间复杂度logn，注意区分n public double myPow(double x, int n) { if(n==0) return 1.0; else if(n<0) return 1/pow(x,-

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \ 3 4 4 3 But the f

Word Search Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, where “adjacent” cells are those horizontally or v

231. Power of Two Given an integer, write a function to determine if it is a power of two. Credits: Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

69. Sqrt(x) Implement int sqrt(int x). Compute and return the square root of x. Subscribe to see which companies asked this question 这道题要找x的平方根，x的平方根肯定小于x/2。要在[1,x/2]有序序列当中找一个数，用二分法：

108. Convert Sorted Array to Binary Search Tree Given an array where elements are sorted in ascending order, convert it to a height balanced BST.    这到题把有序数组转成平衡二叉搜索树，所以选取数组的中点num[mid]作为根，对左右两边分

1.前序 递归 public List<Integer> preorderTraversal(TreeNode root) { List<Integer> list=new ArrayList<Integer>(); if(root!=null){ list.add(root.val); ...