摘要：
Given the head of a singly linked list, reverse the list, and return the reversed list. Example 1: Input: head = [1,2,3,4,5] Output: [5,4,3,2,1] Examp 阅读全文
摘要：
Write an algorithm to determine if a number n is happy. A happy number is a number defined by the following process: Starting with any positive intege 阅读全文