# UVa100 - The 3n + 1 problem
[Prblem link](https://onlinejudge.org/external/1/100.pdf)
## Review
### 題目敘述理解
for each pair determine the maximum cycle length over **all** integers between and including i and j
從 i 到 j一一計算,找最大cycle length。
## Ans
```cpp=
#include <iostream>
using namespace std;
int main(){
int A,B;
while(cin>>A>>B){
int max_length=0;
for(int i=min(A,B);i<=max(A,B);i++){
int cur=i,cur_length=0;
while(cur!=1){
if(cur%2==0) cur/=2;
else cur=cur*3+1;
cur_length++;
}
if(cur_length>max_length)max_length=cur_length;
}
cout<<A<<" "<<B<<" "<<max_length+1<<endl;
}
}
```