There are n different online courses numbered from 1 to n. Each course has some duration(course length) tand closed on dth day. A course should be taken continuously for t days and must be finished before or on the dth day. You will start at the 1st …

There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total number of courses and a l…

There are a total of n courses you have to take, labeled from 0 to n-1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total number of courses and a lis…

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down). Write a function to count the total strobogrammatic numbers that exist in the range of low <= num <= high. For example,Given low = "50&qu…

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers. Ensure that numbers within the set are sorted in ascending order. Example 1…

Implement a basic calculator to evaluate a simple expression string. The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers and empty spaces . The expression string contains only non-nega…

There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total number of courses and a l…

There are a total of n courses you have to take, labeled from 0 to n-1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total number of courses and a lis…

原题链接在这里:https://leetcode.com/problems/course-schedule-ii/ 题目: There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expres…

There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total number of courses and a l…

You are given a binary tree in which each node contains an integer value. Find the number of paths that sum to a given value. The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to…

The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After a tour, the smart thief realized that "all hou…

Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once. For example: Given nums = [1, 2, 1, 3, 2, 5], return [3, 5]. Note: The order…

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the difference between nums[i] and nums[j] is at most t and the difference between i and j is at most k. 这道题跟之前两道Contains Duplicate 包含重复值和Conta…

Design and implement a TwoSum class. It should support the following operations:add and find. add - Add the number to an internal data structure.find - Find if there exists any pair of numbers which sum is equal to the value. For example,add(1); add(…

Implement a MyCalendarThree class to store your events. A new event can always be added. Your class will have one method, book(int start, int end). Formally, this represents a booking on the half open interval [start, end), the range of real numbers …

There is a ball in a maze with empty spaces and walls. The ball can go through empty spaces by rolling up (u), down (d), left (l) or right (r), but it won't stop rolling until hitting a wall. When the ball stops, it could choose the next direction. T…

On a 2 dimensional grid with R rows and C columns, we start at (r0, c0) facing east. Here, the north-west corner of the grid is at the first row and column, and the south-east corner of the grid is at the last row and column. Now, we walk in a clockw…

Implement a basic calculator to evaluate a simple expression string. The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers and empty spaces . The expression string contains only non-nega…

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down). Write a function to count the total strobogrammatic numbers that exist in the range of low <= num <= high. Example: Input: low = "50"…

207. Course Schedule There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total numb…

There are n different online courses numbered from 1 to n. Each course has some duration(course length) t and closed on dth day. A course should be taken continuouslyfor t days and must be finished before or on the dth day. You will start at the 1st …

以前从来没有写过解题报告,只是看到大肥羊河delta写过不少.最近想把写博客的节奏给带起来,所以就挑一个比较容易的题目练练手. 原题链接 https://leetcode.com/problems/course-schedule/ 题目大意 有n个课程,编号分别是0到n-1.我们的目标是修完所有课程.然而有些课程有前置课程的,我们必须修完前置课程才能修该门课程.题目给了我们课程之间的前置关系,让我们判断是否能修完所有课程. 题目原型 这个题目的描述简单粗暴,我们不难发现,其实是给了我们一个有向图…

There are n different online courses numbered from 1 to n. Each course has some duration(course length) t and closed on dth day. A course should be taken continuously for t days and must be finished before or on the dth day. You will start at the 1st…

课程表III 这里有 n 门不同的在线课程,他们按从 1 到 n 编号.每一门课程有一定的持续上课时间(课程时间)t 以及关闭时间第 d 天.一门课要持续学习 t 天直到第 d天时要完成,你将会从第 1 天开始. 给出 n 个在线课程用 (t, d) 对表示.你的任务是找出最多可以修几门课. 示例: 输入: [[100, 200], [200, 1300], [1000, 1250], [2000, 3200]] 输出: 3 解释: 这里一共有 4 门课程, 但是你最多可以修 3 门: 首先,…

630. 课程表 III 这里有 n 门不同的在线课程,他们按从 1 到 n 编号.每一门课程有一定的持续上课时间(课程时间)t 以及关闭时间第 d 天.一门课要持续学习 t 天直到第 d 天时要完成,你将会从第 1 天开始. 给出 n 个在线课程用 (t, d) 对表示.你的任务是找出最多可以修几门课. 示例: 输入: [[100, 200], [200, 1300], [1000, 1250], [2000, 3200]] 输出: 3 解释: 这里一共有 4 门课程, 但是你最多可以修 3…

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the difference between nums[i] and nums[j] is at most t and the difference between i and j is at most k. SOL1: public class Solution { public b…

原题链接在这里:https://leetcode.com/problems/house-robber-iii/ 题目: The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent hous…

原题链接在这里:https://leetcode.com/problems/two-sum-iii-data-structure-design/ 题目: Design and implement a TwoSum class. It should support the following operations: add and find. add - Add the number to an internal data structure.find - Find if there exists…

原题链接在这里:https://leetcode.com/problems/single-number-iii/ 题目: Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once. For example: Giv…