题目 Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most wa...

题目 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. Each solution contains a distinct board configuration of the n-queens' placement, where 'Q'...

题目 Implement int sqrt(int x). Compute and return the square root of x. x is guaranteed to be a non-negative integer. 我的思路 我能想到的只有暴力方法，从一个位置开始，一步一步加一，直到找到平方根。 代码 int mySqrt(int x) { long long times = 0; int y = x; while (y > 0) { y >>= 1; ++times; ...

题目 Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements that appear twice in this array. Could you do it without extra space and in O(n) runtime? Example: Input: [4,3,2,7,8,2,3,1] Output: [2,3] 思路 想了好久，终于想出来了。首先，题...

题目 Given an 2D board, count how many battleships are in it. The battleships are represented with 'X's, empty slots are represented with '.'s. You may assume the following rules: You receive a valid board, made of only battleships or empty slots. Battleships can only be placed horizon...

题目 Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as possible. Note: n is a positive integer, which is in the range of [1, 10000]. All the integers in th...

题目 Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not. You need to merge them into a new binary tree. The merge rule is that if two nodes overlap, then sum node values up as the new value of the me...

题目 Find the contiguous subarray within an array (containing at least one number) which has the largest sum. For example, given the array [-2, 1, -3, 4, -1, 2, 1, -5, 4], the contiguous subarray [4, -1, 2, 1] has the largest sum = 6. 思路一 首先，可以直接两重循环，找到所有的子数组，然后计算出来和最大的那个，时间复杂度为O(n)，空间复杂度为O(1)。代码如下...