OI-codes/S2OJ/165/165.cpp

#include <iostream>

using std::cin;
using std::cout;
const char endl = '\n';

const int N = 1e6 + 5;

int next[N];
std::string s1, s2;

int main() {
    std::ios::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> s1 >> s2;

    next[0] = -1;

    for (int i = 1, j = -1; i < s2.size(); i++) {
        while (~j && s2[j + 1] != s2[i]) j = next[j];

        if (s2[j + 1] == s2[i]) j++;

        next[i] = j;
    }

    for (int i = 0, j = -1; i < s1.size(); i++) {
        while (~j && s1[i] != s2[j + 1]) j = next[j];

        if (s1[i] == s2[j + 1]) j++;

        if (j + 1 == s2.size()) {
            cout << i - j + 1 << endl;
        }
    }

    return 0;
}