模式串匹配,kmp
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include<string.h>
#define MAXSTRLEN 255 /* 可以在255以內定義最大串長 */
typedef char SString[MAXSTRLEN + 1]; /* 0號單元存放串的長度 */
void get_next(SString T, int next[]);
void get_nextval(SString T, int nextval[]);
int Index(SString S, SString T, int pos) {int i = pos; int j = 1;while (i <= S[0] && j <= T[0]) {if (S[i] == T[j]) {++i; ++j;} //繼續比較后繼字符else {i = i - j + 2; j = 1;} //指針后退重新開始匹配
}if (j > T[0]) return i - T[0];else return 0;
}int Index_KMP_1(SString S, SString T, int pos) {int i = pos; int j = 1;int *next = (int *)malloc((T[0] + 1) * sizeof(int));get_next(T, next);while (i <= S[0] && j <= T[0]) {if (j == 0 || S[i] == T[j]) {++i; ++j;} //繼續比較后繼字符else j = next[j]; //模式串向右移動
}free(next);if (j > T[0]) return i - T[0]; //匹配成功else return 0;
}void get_next(SString T, int next[]) {int i = 1, j = 0; next[1] = 0;while (i < T[0]) {if (j == 0 || T[i] == T[j]) {++i; ++j; next[i] = j;}else j = next[j];}
}int Index_KMP_2(SString S, SString T, int pos) {int i = pos; int j = 1;int *nextval = (int *)malloc((T[0] + 1) * sizeof(int));get_nextval(T, nextval);while (i <= S[0] && j <= T[0]) {if (j == 0 || S[i] == T[j]) {++i; ++j;} //繼續比較后繼字符else j = nextval[j]; //模式串向右移動
}free(nextval);if (j > T[0]) return i - T[0]; //匹配成功else return 0;
}void get_nextval(SString T, int nextval[]) {int i = 1; nextval[1] = 0; int j = 0;while (i < T[0]) {if (j == 0 || T[i] == T[j]) {++i; ++j;if (T[i] != T[j]) nextval[i] = j;else nextval[i] = nextval[j];}else j = nextval[j];}
}
/*
樣例
s:ababcabcacbabt:abcac */
int main(){SString S, T;scanf("%s",S+1);S[0]=strlen(S+1);S[S[0]+1]='\0';scanf("%s",T+1);T[0]=strlen(T+1);T[T[0]+1]='\0';printf("Index: %d\n", Index(S, T, 1));//暴力模式匹配方法printf("Index_KMP_1: %d\n", Index_KMP_1(S, T, 1));//KMP算法printf("Index_KMP_2: %d\n", Index_KMP_2(S, T, 1));//KMP優化算法
}
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轉載于:https://www.cnblogs.com/13224ACMer/p/5037883.html
超強干貨來襲 云風專訪:近40年碼齡,通宵達旦的技術人生總結
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