Determine whether a string contains another string (KMP, BF)

Judge whether a string is a substring of another string, that is, the implementation of the strstr () function. A simple implementation method is the BF algorithm.

1. BF algorithm

int BF(char *s, char *p){    if(s==NULL || p==NULL)return -1;    int i=0;    int j;    while(i<strlen(s)){        j=0;        while(s[i]==p[j] && j<strlen(p)){            i++;            j++;        }        if(j==strlen(p))return i-j;        i=i-j+1;    }    return -1;}

2. KMP Algorithm

The principles of the KMP algorithm are explained in many articles, so I won't talk about it (I don't quite understand it ......). The key aspect of the entire KMP algorithm is the implementation of the next array.

KMP algorithm subject:

int KMP(char *s, char *p){    if(s==NULL || p==NULL)return -1;    int next[100];    get_next(next, p);    int i=0;    int j=0;    while(i<strlen(s)){        if(j==-1 || s[i]==p[j]){            i++;            j++;        }else{            j=next[j];        }        if(j==strlen(p))return i-j;    }    return -1;}

Implementation of the get_next function:

void get_next(int *next, char *p){    if(next==NULL || p=NULL)return;    int i=0;    int j=-1;    next[0]=-1;    while(i<strlen(p)-1){        if(j==-1 || p[i]==p[j]){            i++;            j++;            next[i]=j;        }elseP{            j=next[j];        }    }}

Note that the implementation of the get_next function is only related to the sub-string...

Determine whether a string contains another string (KMP, BF)