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题目链接Given a digit string, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the tele... 阅读全文
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题目链接Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.For "(()", the... 阅读全文
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题目链接Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.If such arrangement is not pos... 阅读全文
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题目链接 Given an unsorted integer array, find the first missing positive integer. For example, Given [1,2,0] return 3, and [3,4,-1,1] return 2. Your algorithm should run in O(n) time and uses con... 阅读全文