摘要：
Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: A partially filled sudoku which 阅读全文
摘要：
Implement strStr(). Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Example 1: Example 2: 在一个 阅读全文
摘要：
Implement pow(x, n). 求x的n次幂，如果用n个循环相乘，那就太简单了，肯定不是这题要考察的。 解法：利用性质： n是奇数，n % 2 == 1, x^n = x^(n/2) * x^(n/2) * x;n是偶数，n % 2 == 0, x^n = x^(n/2) * x^(n/2 阅读全文
摘要：
Given a string s, find the longest palindromic subsequence's length in s. You may assume that the maximum length of s is 1000. Example 1:Input: Output 阅读全文
摘要：
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example,"A man, a plan, a canal: Pan 阅读全文
摘要：
Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest l 阅读全文
摘要：
The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order,We get the following sequence 阅读全文
摘要：
Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers. If such arrangement is not possib 阅读全文
摘要：
Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example,[1,1,2] have the following unique pe 阅读全文
摘要：
Given a collection of numbers, return all possible permutations. For example,[1,2,3] have the following permutations:[1,2,3], [1,3,2], [2,1,3], [2,3,1 阅读全文
摘要：
Given two integers n and k, return all possible combinations of k numbers out of 1 ... n. For example,If n = 4 and k = 2, a solution is: 给两个数字n, k，返回所 阅读全文