C++代码

#include<iostream>
using namespace std;
int main()
{
    int n, m;
    cin >> n >> m;
    int cnt = 0;
    for(int i = n; i <= m; i++)
    {
        int x = i;
        while(x)
        {
            if(x % 10 == 2) cnt ++;
            x = x / 10;
        }
    }
    cout << cnt << endl;
    return 0;
}