GFG RABIN KARP

#include <bits/stdc++.h>
using namespace std;

#define d 256
 
void search(char pat[], char txt[], int q) {
    int M = strlen(pat);
    int N = strlen(txt);
    int i, j;
    int p = 0; // hash value for pattern
    int t = 0; // hash value for txt
    int h = 1;

    for (i = 0; i < M - 1; i++)
        h = (h * d) % q;
    for (i = 0; i < M; i++) {
        p = (d * p + pat[i]) % q;
        t = (d * t + txt[i]) % q;
    }

    for (i = 0; i <= N - M; i++) {

        if ( p == t ) {  

            for (j = 0; j < M; j++)
            {
                if (txt[i+j] != pat[j])
                {
                  flag = false;
                  break;
                }
                  if(flag)
                  cout<<i<<" ";
                      
            }
           
            if (j == M)
                cout<<"Pattern found at index "<< i<<endl;
        }

        if ( i < N-M ){
            t = (d*(t - txt[i]*h) + txt[i+M])%q;
            if (t < 0)
            t = (t + q);
        }
    }
}
 
int main() {
    char txt[] = "GEEKS FOR GEEKS";
    char pat[] = "GEEK";
    int q = 101;
    search(pat, txt, q);
    return 0;
}