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Given a binary tree, return the vertical order traversal of its nodes values. For each node at position (X, Y), its left and right children respective 阅读全文
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The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return the 阅读全文
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The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return all 阅读全文
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Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used. Note: Example 1: Example 2: 阅读全文
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Reverse bits of a given 32 bits unsigned integer. Example 1: Example 2: Note: Note that in some languages such as Java, there is no unsigned integer t 阅读全文
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Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1. Examples: Note: You may assume the 阅读全文
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The Hamming distance between two integers is the number of positions at which the corresponding bits are different. Now your job is to find the total 阅读全文
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The Hamming distance between two integers is the number of positions at which the corresponding bits are different. Given two integers x and y, calcul 阅读全文
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Given an integer (signed 32 bits), write a function to check whether it is a power of 4. Example 1: Input: 16 Output: true Example 2: Input: 5 Output: 阅读全文
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Given an integer, write a function to determine if it is a power of three. Example 1: Example 2: Example 3: Example 4: Follow up:Could you do it witho 阅读全文