#include <bits/stdc++.h>
using namespace std;

int main() {
    int n, x, count = 0;
    cin >> n >> x;

    for (int i = 1; i <= n; i++) {
        int temp = i;
        while (temp > 0) {
            if (temp % 10 == x) {
                count++;
            }
            temp /= 10;
        }
    }

    cout << count << endl;
    return 0;
}

import java.util.Scanner; import java.util.ArrayList; public class Main2 {

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    ArrayList<Integer> list = new ArrayList<>();

    //表示1到n的n
    int n = sc.nextInt();

    //表示要计数的数字
    int x = sc.nextInt();

    //集合中添加1到n的n
    for (int i = 1; i <= n; i++) {
        list.add(i);
    }

    //遍历集合，计算其中出现多少次x
    int count = 0;
    for (int i = 0; i < list.size(); i++) {
        //用一个临时变量temp来存储当前元素的值
        int temp = list.get(i);

        //计算temp里有几个x
        while (temp > 0) {
            if (temp % 10 == x) {
                count++;
            }
            temp = temp / 10;
        }
    }
    System.out.println(count);
}

}

[NOIP 2013 普及组] 计数问题

#include <iostream>
using namespace std;

int countDigit(int n,int x)
{
  int count = 0;
  for(int base = 1;base<=n;base*=10)
  {
    int high = n/(base*10);
    int low = n%base;
    int curr = (n/base) % 10;
    if(x == 0){
      if(high>0)
      {
        high--;
      }
      else {
        break;
      }
    }
    count += high * base;
    if(curr == x)
    {
      count += low + 1;
    }
    else if(curr > x)
    {
      count += base;
    }
  }
  return count;
}

int main()
{
  int n,x;
  cin>>n>>x;
  cout<< countDigit( n,  x) << endl;
  return 0;
}