题解 | #自守数#

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int main() {
    int n, cnt = 0;
    cin >> n;
    string stri, strs;
    for (int i = 0; i <= n; ++i)
    {
        stri = to_string(i);
        strs = to_string(i * i);
        reverse(stri.begin(), stri.end());
        reverse(strs.begin(),strs.end());
        if (strs.find(stri) == 0)
        {
            ++cnt;
        }
    }
    cout << cnt; 
    return 0;
}