题解 | #自守数#

#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
using namespace std;

/*
25
5
*/
bool compare_num(string a, string b) {
    reverse(a.begin(), a.end());
    reverse(b.begin(), b.end());
    int n = a.size();
    for (int i = 0; i < n; i++) {
        if (a[i] != b[i]) {
            return false;
        }
    }
    return true;
}

int main() {
    int n;
    cin >> n; 
    int n_2;
    int res = 0;
    for (int i = 0; i <= n; i++) {
        n_2 = pow(i, 2);
        if (compare_num(to_string(i), to_string(n_2))) {
            res++;
        }
           
    }
    cout << res;
}
// 64 位输出请用 printf("%lld")

不聪明