摘要：
Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. 解法1： 采用递归的方法，不管合并几个，归根到底还是需要两两合并。 首先想到的是前两个先合并，然后再跟 阅读全文
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Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses. For example, given n = 3, a solution set is: 解 阅读全文
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Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists. 解法： 新建一个 阅读全文
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Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the 阅读全文
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Given a linked list, remove the nth node from the end of list and return its head. For example, Note:Given n will always be valid.Try to do this in on 阅读全文
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Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array whic 阅读全文
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Given a digit string, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telepho 阅读全文
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Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. 阅读全文
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Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of 阅读全文
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Write a function to find the longest common prefix string amongst an array of strings. 解法: 广度优先搜索：先比较所有字符串的第一个字符，然后比较第二个。。。。如果某一行没有了（说明其为最短的单词）或者遇到不匹配 阅读全文