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7. Reverse Integer Medium Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 阅读全文
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1569. Number of Ways to Reorder Array to Get Same BST Hard 1590185Add to ListShare Given an array nums that represents a permutation of integers from 阅读全文
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1351. Count Negative Numbers in a Sorted Matrix Easy 338393Add to ListShare Given a m x n matrix grid which is sorted in non-increasing order both row 阅读全文
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如何求取两个数字的最大公约数？ 原理：a和b的最大公约数，也是a和a%b的最大公约数 private int gcd(int a, int b) { //如果b为0，那么直接返回a if(b == 0) return a; //如果a可以被b整除，那么返回b if(a % b == 0) retur 阅读全文
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1438. Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit Medium 2790115Add to ListShare Given an array of integers nums and an 阅读全文
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什么是质数？在一个大于1的自然数中，除了1和此整数自身外，没法被其他自然数整除的数，比如：2,3,5,7,11... 什么是合数？比1大但不是素数的数称为合数。1和0既非素数也非合数。合数是由若干个质数相乘而得到的， 比如：4,6,8,9,10... 如何判定一个数是否位质数？ public cla 阅读全文
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834. Sum of Distances in Tree Hard There is an undirected connected tree with n nodes labeled from 0 to n - 1 and n - 1 edges. You are given the integ 阅读全文
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1359. Count All Valid Pickup and Delivery Options Hard 1674150Add to ListShare Given n orders, each order consist in pickup and delivery services. Cou 阅读全文
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数据库：append only 何为数据库？写个shell脚本，set的时候追加纪录，get的时候grep and tail 最新纪录，即为一个数据库#!/bin/bashdb_set () { echo "$1,$2" >> database} db_get () { grep "^$1," da 阅读全文
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2246. Longest Path With Different Adjacent Characters Hard You are given a tree (i.e. a connected, undirected graph that has no cycles) rooted at node 阅读全文