Given an integer n, generate a square matrix filled with elements from 1 to _n_2 in spiral order. 思路：仿佛回到高一的那个暑假。。。 /* *********************************************** Author :111qqz Created Time :2017年04月11日 星期二 18时52分15秒 File Name :59.cpp ************************************************ */ class Solution { public: int …

Follow up for "Unique Paths": Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 and 0 respectively in the grid. For example, There is one obstacle in the middle of a 3x3 grid as illustrated below. [ [0,0,0], [0,1,0], [0,0,0] …

Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path. Note: You can only move either down or right at any point in time. 数字三角形。。。。从坐上到右下问最短路径。。每次只能向下或者向右。。。 wa了一次。。。是因为边界值赋值成了0.。。求最短路径显然因为赋值成inf才对orz..果然傻了。。 简单的dp我们简单的A. 顺便吐 …

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place. click to show follow up. **Follow up:**Did you use extra space? A straight forward solution using O(m__n) space is probably a bad idea. A simple improvement uses O(m + n) space, but still not the best solution. Could you …

Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i]. Solve it without division and in O(n). For example, given [1,2,3,4], return [24,12,8,6]. Follow up: Could you solve it with constant space complexity? (Note: …

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 vertically neighboring. The same letter cell may not be used more than once. 思路：dfs即可。记得要回溯一下... /* …

Follow up for "Remove Duplicates": What if duplicates are allowed at most twice? For example, Given sorted array nums = [1,1,1,2,2,3], Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3. It doesn't matter what you leave beyond the new length. Subscribe to see …

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). Write a function to determine if a given target is in the array. The array may contain duplicates. 好像阿里一面的时候问过。。。 思路：肯定是二分。。。不过由于有重复元素。。。所以很恶心。。。 总的思路是。。。当发现重复元素。。并且该重复元素不 …

According to the Wikipedia's article: "The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970." Given a board with m by n cells, each cell has an initial state live (1) or dead (0). Each cell interacts with its eight neighbors …

Given a collection of integers that might contain duplicates, nums, return all possible subsets. Note: The solution set must not contain duplicate subsets. For example, If nums = [1,2,2], a solution is: [ [2], [1], [1,2,2], [2,2], [1,2], [] ] 思路： 复习（？）一下 枚举子集的三种写法 （还有种更飘逸的...先不写了orz 这道题我用位向量法A的。。 /* …