Maintain a variable to manage how many first characters of \(S\) has been typed, while scanning the characters of \(T\).

Sample code

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

int main() {
    string s, t;
    cin >> s >> t;
    int n = s.size();
    int m = t.size();
    vector<int> a(n);
    int j = 0;
    for (int i = 0; i < m; i++) {
        if (s[j] == t[i]) {
            a[j] = i + 1;
            j++;
        }
    }
    for (int i = 0; i < n; i++) cout << a[i] << " \n"[i == n - 1];
}