题解 | 记数问题

字符串解法：

#include <iostream>
using namespace std;

int main() {
    int n, x;
    std::cin >> n >> x;
    std::string s;
    int count = 0;
    for (int i = 1; i <= n; ++i) {
        s = std::to_string(i);
        for (char c : s) {
            if (c == '0' + x) {
                ++count;
            }
        }
    }
    std::cout << count << std::endl;
}
// 64 位输出请用 printf("%lld")