摘要：
Determine whether an integer is a palindrome. Do this without extra space.（不要使用额外的空间） Some hints: Could negative integers be palindromes? (ie, -1) If 阅读全文
摘要：
Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest l 阅读全文
摘要：
Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level). For example: Given binary tree [ 阅读全文
摘要：
Given a binary tree, return the inorder traversal of its nodes' values. For example: Given binary tree [1,null,2,3], return [1,3,2]. Note: Recursive（递 阅读全文