Rabin-Karp

#include <bits/stdc++.h>
#define MAXN 2000001
#define P 73
#define MOD1 100007
#define MOD2 100021

using namespace std;

ifstream fin ("strmatch.in");
ofstream fout ("strmatch.out");

string A, B;
int NA, NB;
int hashA1, hashA2, P1, P2;
char match[MAXN];

int main() {
    fin >> A >> B;
    NA = A.size(), NB = B.size();
    if (NA > NB) {
        fout << "0\n";
        return 0;
    }

    P1 = P2 = 1;
    hashA1 = hashA2 = 0;
    for (int i = 0; i < NA; i ++) {
        hashA1 = (hashA1 * P + A[i]) % MOD1;
        hashA2 = (hashA2 * P + A[i]) % MOD2;
        if (i != 0)
            P1 = (P1 * P) % MOD1, P2 = (P2 * P) % MOD2;
    }

    int hash1 = 0, hash2 = 0;
    for (int i = 0; i < NA; i++)
        hash1 = (hash1 * P + B[i]) % MOD1, hash2 = (hash2 * P + B[i]) % MOD2;

    int Nr = 0;
    if (hash1 == hashA1 && hash2 == hashA2)
        match[0] = 1, Nr ++;

    for (int i = NA; i < NB; i ++) {
        hash1 = ((hash1 - (B[i - NA] * P1) % MOD1 + MOD1) * P + B[i]) % MOD1;
        hash2 = ((hash2 - (B[i - NA] * P2) % MOD2 + MOD2) * P + B[i]) % MOD2;
        if (hash1 == hashA1 && hash2 == hashA2)
            match[ i - NA + 1 ] = 1, Nr ++;
    }
    fout << Nr << '\n';

    Nr = 0;
    for (int i = 0; i < NB && Nr < 1000; i ++)
        if (match[i])
            Nr ++, fout << i << ' ';
    return 0;
}