题解 | #自守数#

#include <iostream>
using namespace std;

int main() {
    int n;
    while (cin >> n) { 
        int cnt = 0;
        for (int i = 0; i <= n; ++i){
            if (i % 10 == 0 || i % 10 == 1 || i % 10 == 5 || i % 10 == 6){
                string str1 = to_string(i);
                string str2 = to_string(i * i);
                int pos = str2.size() - str1.size();
                if (str2.find(str1, pos) != string::npos){
                    ++cnt;
                }
            }
        }
        cout << cnt << endl;
    }
    return 0;
}