摘要：
Invert a binary tree. 4 / \ 2 7 / \ / \ 1 3 6 9 to 4 / \ 7 2 / \ / \ 9 6 3 1 Trivia:This problem was inspired by this original tweet by Max Howell: Go 阅读全文
摘要：
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, n] 阅读全文
摘要：
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 one of 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