题目描述: There are n bulbs that are initially off. You first turn on all the bulbs. Then, you turn off every second bulb. On the third round, you toggle every third bulb (turning on if it's off or turning off if it's on). For the ith round, you toggle e…

LeetCode:二进制求和[67] 题目描述 给定两个二进制字符串,返回他们的和(用二进制表示). 输入为非空字符串且只包含数字 1 和 0. 示例 1: 输入: a = "11", b = "1" 输出: "100" 示例 2: 输入: a = "1010", b = "1011" 输出: "10101" 题目分析 分三部分分别运算.考虑进位值: Java题解 class Solut…

[L4]N-Queens 解题报告 N-Queens Total Accepted: 16418 Total Submissions: 63309 My Submissions 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 so…

六月箴言 万物之中,希望最美:最美之物,永不凋零.—— 斯蒂芬·金 第二周算法记录 007 -- Reverse Integer (整数反转) 题干英文版: Given a 32-bit signed integer, reverse digits of an integer. Example 1: Input: 123Output: 321 Example 2: Input: -123Output: -321 Example 3: Input: 120Output: 21 Note:Assum…

Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id. +----+------------------+ | Id | Email | +----+------------------+ | 1 | john@example.com | | 2 | bob@example.com |…

已知$f(x)=ax^2+bx+c$在$x\in\{-1,0,1\}$时满足$|f(x)|\le1$ 求证:当$|x|\le1$时$|f(x)|\le\frac{5}{4}$. 证明: $$f(x)=\frac{1}{2}f(-1)(x^2-x)-f(0)(x^2-1)+\frac{1}{2}f(1)(x^2+x)$$ $$\le\frac{1}{2}|x|(1-x+x+1)+1-x^2$$ $$\le 1+|x|-x^2\le\frac{5}{4}$$ 评:1由局部的几个点可以判断一个区域的性…

Longest Palindromic Substring -- HARD 级别 Question SolutionGiven 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 substring. 经典的DP题目. 主页君给出3种解…

Reverse Integer 题目要求:给定一个int 类型值,求值的反转,例如以下: Example1: x = 123, return 321      Example2: x = -123, return -321 简单问题一般蕴含细节的处理.思路非常easy,直接贴Java程序: public class Solution { public int reverse(int x) { int head = x/10; int tail = x%10; long re = 0; while…

题目: Given a set of distinct integers, S, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example,If S = [1,2,3], a solution is: [ [3], [1], [2], [1,2,3]…

题目: Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below. For example, given the following triangle [ [], [,4], [6,,7], [4,,8,3] ] The minimum path sum from top to bottom is 11 (i…