题解 | 反序相等

#include <iostream>
using namespace std;

int reverse(int n) {
    int t = n;
    int count = 0;
    while (t) {
        count++;
        t /= 10;
    }
    t = n;
    int a[count];
    for (int i = 0; i < count; i++) {
        a[i] = t % 10;
        t /= 10;
    }
    t = 0;
    for (int i = 0; i < count; i++) {
        t += a[i];
        t *= 10;
    }
    return t / 10;
}

int main() {
    bool flag = false;
    for (int i = 1000; i < 10000; i++) {
        if (i * 9 == reverse(i))     {
            cout << i << endl;
            flag = true;
        }
    }
    if (!flag)   cout << "无" << endl;
}
// 64 位输出请用 printf("%lld")