KMP

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#include<stdio.h> #include<iostream> #include<string.h> using namespace std;   void GetNext(char *str,int next[]) {     int j,k;     j=0;k=-1;next[0]=-1;     while(str[j]!='\0')     {         if(k==-1 || str[j]==str[k])         {             j++;k++;             next[j]=k;         }         else k=next[k];     } }   int KMPIndex(char *s,char *t) {     int lent=strlen(t);     int next[100],i=0,j=0,v;     GetNext(t,next);     while(s[i]!='\0' && t[j]!='\0')     {         if(j==-1 || s[i]==t[j])         {             i++;j++;         }         else j=next[j];     }     if(j>=lent) v=i-lent;     else v=-1;     return v; }   int main() {     char s[]="ababcabsds";     char t[]="abcd";     cout<<KMPIndex(s,t);     return 0; }