@[IKUNNN](/user/952739) 数字长度不是一定的
by that_summer @ 2023-07-20 20:07:59
你可以看看数据范围1≤L≤R≤100000
```c
if(i%10==2)
{
r++;
}
if(i/10%10==2)
{
r++;
}
if(i/100%10==2)
{
r++;
}
```
这最多能求个十百位的数吧
by YC_George @ 2023-07-20 20:12:40
@[IKUNNN](/user/952739) 得把区间 $[l,r]$ 中的每一个数的每一位都枚举出来，再统计个数。
代码如下：
```cpp
#include<bits/stdc++.h>
using namespace std;
int f(int x){
int sum=0;
while(x){
if(x%10==2){
sum++;
}
x/=10;
}
return sum;
}
int main(){
int l,r,ans=0;
cin>>l>>r;
for(int i=l;i<=r;i++){
ans+=f(i);
}
cout<<ans;
return 0;
}
```
求关注
by that_summer @ 2023-07-20 20:13:12
```c
while(q){
int t = q%10;
q/=10;
if(t==2)p++;
}
```
每一个数都这样就行啦
by YC_Aldrich @ 2023-07-20 20:13:48
@[that_summer](/user/830170) 谢谢几位大佬的指点，关注了！！
by RTF_Sonetto @ 2023-07-21 08:30:35
@[YC_Aldrich](/user/995025) 谢谢几位大佬的指点，关注了！！
by RTF_Sonetto @ 2023-07-21 08:30:55
@[YC_George](/user/1004860) 谢谢几位大佬的指点，关注了！！
by RTF_Sonetto @ 2023-07-21 08:31:12
```cpp
#include<bits/stdc++.h>
#include <cmath>
using namespace std;
int main()
{
int a,b,s=0;
cin>>a>>b;
for(int i=a;i<=b;i++){
int t=i;
for(int j=1;t>0;j++){
if(t%10==2){
s++;
}
t=t/10;
}
}
cout<<s;
return 0 ;
}
```
by yuwuyanqiu @ 2023-08-08 08:57:34
都好厉害
by Cjq0626 @ 2023-08-14 10:56:54
```
#include<iostream>
using namespace std;
int l,r,ans;
void lr(int x){
int y;
while(x){
y = x % 10;
x /= 10;
if(y == 2){
ans ++;
}
}
}
int main(){
cin >> l >> r;
for(int i = l ;i <= r;i ++){
lr(i);
}
cout << ans;
return 0;
}
```
by zqhbxsgs @ 2023-08-26 23:03:08