【算法学习】KMP查找匹配字符串

来源：互联网发布：银临和灰原穷夫妇知乎编辑：程序博客网时间：2024/06/04 18:06

#include <stdio.h>#include <stdlib.h>#include <string.h>int GenNext(char *mod, int len, int next[]){if (mod == NULL || next == NULL || len <= 0)return -1;next[0] = -1;int k = -1;int j = 0;while (j < len - 1){if (k == -1 || mod[k] == mod[j]){k++;j++;next[j] = next[k] + 1;}else{k = next[k];}}return 1;}int KmpSearch(char *text, char *mod){if (text == NULL || mod == NULL)return -1;int modlen = strlen(mod);int *next = (int *)malloc(sizeof(int) * modlen);if (!next){return -1;}if (GenNext(mod, modlen, next) < 0)return -1;int i = 0, j = 0;int textlen = strlen(text);while (i < textlen && j < modlen && j != -1){if (text[i] == mod[j]){i++;j++;}else{j = next[j];}}free(next);if (j == modlen)return i - j;elsereturn -1;}int main(int argc, char *argv[]){char text[256], mod[16];printf("Please input text:");scanf("%s", text);printf("Please input mod:");scanf("%s", mod);int index = KmpSearch(text, mod);printf("Index[%d] OK\n", index);return 0;}

主要思路是先用一个next数组保存模式字符串的最长前缀后缀字符串，在匹配时就可以根据next数组快速匹配，时间复杂度O(n+m), 空间复杂度O(m).

具体详见http://blog.csdn.net/v_july_v/article/details/7041827

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