James Pan

原题网址：https://leetcode.com/problems/happy-number/ Write an algorithm to determine if a number is "happy". A happy number is a number defined by the following process: Starting with any positive

原题网址：https://leetcode.com/problems/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