CSP-S 2022 T16

#include <iostream> 
#include <string> 
#include <vector> 

using namespace std; 
  
int f(const string &s, const string &t) 
{ 
    int n = s.length(), m = t.length(); 

    vector<int> shift(128, m + 1); 

    int i, j;

    for (j = 0; j < m; j++)
        shift[t[j]] = m - j;

    for (i = 0; i<= n - m; i += shift[s[i + m]]){
        j = 0;
        while(j < m && s[i + j] == t[j]) j++;
        if (j == m) return i;
    }

    return -1;
}

int main()
{
    string a, b;
    cin >> a >> b;
    cout << f(a, b) << endl;
    return 0;
}