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Leetcode#28 Implement strStr()

原题地址

 

因为是道简单题,所以最简单的字符串匹配应该也能过,但还是练习一下KMP算法为好。KMP算法的介绍可以参考这篇

以后有时间试试Boyer-Moore算法

代码:

 1 int strStr(char *haystack, char *needle) { 2   if (!needle[0]) return 0; 3   int n = strlen(needle); 4   int *next = new int[n + 1]; 5   int i, j; 6  7   i = 0; 8   j = -1; 9   next[0] = -1;10   while (needle[i]) {11     if (j < 0 || needle[i] == needle[j]) {12       i++;13       j++;14       next[i] = j;15     }16     else17       j = next[j];18   }19 20   i = 0;21   j = 0;22   while (haystack[i] && j < n) {23     if (j < 0 || haystack[i] == needle[j]) {24       i++;25       j++;26     }27     else28       j = next[j];29   }30 31   return j == n ? i - n : -1;32 }

 

Leetcode#28 Implement strStr()