Happy Number

    1#include <bits/stdc++.h>
    2using namespace std;
    3typedef long long ll;
    4int main() {
    5    ios::sync_with_stdio(0); cin.tie(0); 
    6    string s; cin >> s;
    7    int mx = 1e6;
    8    auto happy = [&] (string ss) {
    9        int cnt = 0;
    10        for (int i = 0; i < ss.size(); i++) {
    11            int c  = ss[i] - '0';
    12            cnt += c * c;
    13        }
    14        
    15        return to_string(cnt);
    16    };
    17    while (mx--) {
    18        if (stoi(s) == 1) {
    19            cout << "Yes" << '\n';
    20            return 0;
    21        }
    22        s = happy(s);
    23    }
    24    cout << "No" << '\n';
    25    return 0;
    26}
    27