What is the optimal way to solve FLOW004 or LUCKYFOUR?

general
,
1

I’ve solved the FLOW004 with the following code. However I’m unhappy with the solution I’ve come up with. I’m just getting started hence don’t know the tools to solve it in a better way.

#include <bits/stdc++.h> 

using namespace std;

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int t;
	cin>>t;
	while(t--)
	{
	    int n, n1, n2;
	    cin>>n;
	    
	    n1 = n%10;
	    n/=10;
	    while(n)
	    {
	        n2 = n%10;
	        n/=10;
	        
	    }
	    
	    cout<<n1+n2<<"\n";
	    
	}

}

Perhaps a better method will be to treat the number as a string and then take the first and last element? This will eliminate the need of a loop and make it faster for longer numbers, giving it a constant complexity instead of O(n);
Please help. Thanks!

2

Inputting takes O(log(n)) time, and so does your code.
But you can alternatively do this

#include <bits/stdc++.h> 
using namespace std;
int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int t;
	cin>>t;
	while(t--){
	    string n;
	    cin>>n;
	    cout<<n[0] + n[n.size()-1] - 2*'0'<<"\n";
	}
}