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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 with the character '.'.A partially filled sudoku which... 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.分析不能用除法，所以使用减法不断减 除数，同时对 除数 倍乘，进行加速除数：3 -> 6 -> 12 ...边界条件：1 除数为0，溢出2 被除数 INT_MIN，同时除数 -1，... 阅读全文
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Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.For "(()", the longest valid parentheses substring is "()", which ha... 阅读全文
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Given an array of integers sorted in ascending order, find the starting and ending position of a given target value.Your algorithm's runtime complexity must be in the order of O(log n).If the target i... 阅读全文
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Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).You are given a target value to search. If found in the a... 阅读全文
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Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.If such arrangement is not possible, it must rearrange it as the lowest possible ord... 阅读全文
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You are given a string, s, and a list of words, words, that are all of the same length. Find all starting indices of substring(s) in s that is a concatenation of each word in words exactly once and wi... 阅读全文
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KMP背景分析普通算法（遍历），会遗忘所有之前比较过的信息，导致每一次移位，都要重新重头比较每一个字符。这将会导致 O(mn)的时间复杂度（m: 关键字符长度，n: 文本string的长度）而KMP算法，则能够保证不去重复比较已经部分匹配的字符，比如序列“abcdabac”，如果“abcd”部分匹配了文本，而在接下来的“a”位置上不匹配，那么算法则会直接跳过4个位置，重新进行比较，而不是移位1个，... 阅读全文
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Implement strStr().Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.分析这就是字符串匹配算法算法一：brute forcetime complexity: O(nm)space complexity: O(1)12345... 阅读全文
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Given a linked list, swap every two adjacent nodes and return its head.For example,Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only constant space. You may not... 阅读全文