kmp

This time p [i]= P [j+1], when the array does not match, the j=next [j] statement is executed. Because of the mismatch, j will go back until j goes back to 0.

The code of kmp is as follows

 //Substring and long string subscripts start from 1
 bool  kmp ( char *s, int l1, char *p, int l2) {
     /*Find next array*/
     for ( int i= two , j= zero ; i<=l1;i++){
         while (j&&p[i]!=p[j+ one ]) j=next[j];
         if (p[i]==p[j+ one ]) j++;
 next[i]=j;
 }
     /*Make string pairing*/
     for ( int i= zero ; i<l1;i++){
         while (j<l2&&s[i]==p[j+ one ]) j++;
         if (j==l2){
             cout << "Matching succeeded" << endl ;
             return  true ;
 }
 j=next[j];
 }
 }