算法模板之KMP

KMP

#include<cstdio>
#include<cstring>
void get_next(char *p,int *next){
    int pLen = strlen(p);
    next[0] = -1;
    int k = -1,j = 0;
    while(j < pLen - 1){
        if(k == -1 || p[j] == p[k]){
            j ++;
            k ++;
            next[j] = k;
        }
        else {
            k = next[k];
        }
    }
}
int kmp(char *s, char * p, int *next){
    int sLen = strlen(s);
    int pLen = strlen(p);
    int i = 0, j = 0;
    while(i < sLen && j < pLen){
        if(j == -1 ||s[i] == p[j]){
            i ++;
            j ++;
        }
        else {
            j = next[j];
        }
    }
    if(j == pLen){
        return i - j;
    }
    else return -1;
}
int main()
{
    char s1[123] = "ggbbaacda";
    char s2[123] = "aadd";
    int next[123] ;
    get_next(s2,next);
    printf("%d\n",kmp(s1,s2,next));
    return 0;
}