摘要：
Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? 判断链表是否带环，我们可以采用在头结点设两个指针，一个叫fast，一个叫slo 阅读全文
摘要：
Given two binary trees, write a function to check if they are equal or not. Two binary trees are considered equal if they are structurally identical a 阅读全文
摘要：
Given a binary tree, return the postorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [3,2,1]. Note: Re 阅读全文
摘要：
Given a binary tree, return the preorder traversal of its nodes' values. Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [1,2,3]. Note: Recursive soluti 阅读全文