线上OJ:
一本通:http://ybt.ssoier.cn:8088/problem_show.php?pid=1949 (opens in a new tab)
Acwing:https://www.acwing.com/problem/content/443/ (opens in a new tab)
相似题目:2013NOIP普及组真题 1. 计数问题 (opens in a new tab)
本题与之一样,由于数据范围不大,直接暴力即可
暴力
#include <bits/stdc++.h>
using namespace std;
int l, r, ans = 0;
int main()
{
scanf("%d %d", &l, &r);
for(int i = l; i <= r; i++)
{
int k = i;
while(k)
{
if( k%10 == 2 ) ans++;
k /= 10;
}
}
printf("%d", ans);
return 0;
}