题解 | 记数问题

#include <iostream>
using namespace std;

int count(int n,int x){
    int sum2 = 0;
    while(n>0){
      if(n%10==x){
        sum2++;
      }
      n/=10;
    }
    return sum2;
}

int main() {
   int n,x;
   cin >> n >> x;
   int sum = 0;
   while(n>0){
    sum+=count(n,x);
    n--;
   }
   cout << sum;
}