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Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything 阅读全文
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Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequ 阅读全文
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Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, where "adjac 阅读全文
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A message containing letters from A-Z is being encoded to numbers using the following mapping: Given an encoded message containing digits, determine t 阅读全文
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Given an array of strings, group anagrams together. For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"], Return: 思路1： 用collections.defaultd 阅读全文
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Given a string s and a non-empty string p, find all the start indices of p's anagrams in s. Strings consists of lowercase English letters only and the 阅读全文
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Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining. 阅读全文
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Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. The Sudoku board could be partially filled, where empty cells are filled wit 阅读全文
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The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font 阅读全文
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Divide two integers without using multiplication, division and mod operator. If it is overflow, return MAX_INT. 思路，不用乘除和mod实现除法，比较容易的想到二分法。需要注意的是，sum+ 阅读全文