ПОиск подстроки

#include <iostream>
#include <vector>
#include <algorithm>
#include <tuple>

using namespace std;

vector<int> zfunc(const string& s){
    vector<int> z(s.size());
    int first = 0;
    int last = 1;
    for (int i = 1; i < s.size(); ++i){
        if (i >= first && i < last && z[i - first] + i < last){
            z[i] = z[i - first];
        } else {
            z[i] = max(0, last - i);
            first = i;
            while (s[i + z[i]] == s[z[i]] && i + z[i] < s.size()){
                ++z[i];
            }
            last = i + z[i];
        }
    }
    return z;
}

int main() {
    string s1, s2;
    cin >> s1 >> s2;
    string s = s2 + "#" + s1;
    vector<int> z = zfunc(s);
    for (size_t i = s2.size() + 1; i < s.size(); ++i){
        if (z[i] == s2.size()){
            cout << i - s2.size() - 1 << " ";
        }
    }
    return 0;
};