题目：

https://www.luogu.com.cn/problem/P1179

 

思路：直接暴力过

代码：

#include<iostream>
using namespace std;
int cnt(int x)
{int sum = 0;while(x){int temp = x %10;if(temp == 2){sum++;}x = x/10;}return sum;
}
int main(void)
{int L,R;cin >> L >> R;int S = 0;for(int i = L ; i <= R ; i++){S = S + cnt(i);}cout << S; return 0;}