摘要： 题目： Given a non-negative integer num, repeatedly add all its digits until the result has only one digit. For example: Given num = 38, the process is l 阅读全文

摘要： 题目： Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements of [1, 阅读全文

摘要： 题目： Invert a binary tree. 4 / \ 2 7 / \ / \ 1 3 6 9 to 4 / \ 7 2 / \ / \ 9 6 3 1 代码： Invert a binary tree. 自己的（递归实现）： 别人的： 自己的（使用队列，非递归实现）: 非递归和递归的在Le 阅读全文

摘要： 题目： Given a word, you need to judge whether the usage of capitals in it is right or not. We define the usage of capitals in a word to be right when on 阅读全文

摘要： 题目： 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 farthe 阅读全文

摘要： 题目： Given a binary array, find the maximum number of consecutive 1s in this array. Example 1: Note: The input array will only contain 0 and 1. The len 阅读全文

摘要： 题目： Given an array of integers, every element appears twice except for one. Find that single one. Note:Your algorithm should have a linear runtime com 阅读全文

摘要： 题目： You are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 阅读全文

摘要： 题目： anysubsequence of the other strings. A subsequence is a sequence that can be derived from one sequence by deleting some characters without changin 阅读全文

摘要： 题目： Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array. Example 1: Input: 3 / \ 9 20 / \ 15 7 阅读全文