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At the beginning of every day, the first person who signs in the computer room will unlock the door, and the last one who signs out will lock the door 阅读全文
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Given two strings s and t, write a function to determine if t is an anagram of s. For example, s = "anagram", t = "nagaram", return true. s = "rat", t 阅读全文
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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
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Invert a binary tree. to 题目大意： 翻转一棵二叉树。 测试样例见题目描述。 花絮： 这道题目的灵感来自于Max Howell的推特原文： Google：我们90%的工程师在用你写的软件（Homebrew），但你竟然不会在白板上翻转一棵二叉树，所以滚吧。 解题思路： 递归或者 阅读全文
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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 ston 阅读全文