C :

#include <stdio.h>

int main()
{
	int t;
	int a, b, ra, rb;
	int sum, rsum;
	scanf("%d", &t);

	while (t--)
	{
		scanf("%d %d", &a, &b);
		rsum = ra = rb = 0;
		while (a)
		{
			ra = ra * 10 + a % 10;
			a /= 10;
		}

		while (b)
		{
			rb = rb * 10 + b % 10;
			b /= 10;
		}
		
		sum = ra + rb;

		while (sum)
		{
			rsum = rsum * 10 + sum % 10;
			sum /= 10;
		}

		printf("%d\n", rsum);
	}
	return 0;
}

C++ :

#include<iostream>
#include<cmath>
using namespace std;

int change(int n)
{   int m=n,s=0,t=1;
    while(n)
    {   n/=10;
        t++;
    }
    while(m)
    {   s=s+m%10*(int)pow(10.0,t-2);
        m/=10;
  t--;
    }
return s;
}   
int main()
{
    int n,s,a,b;
    cin>>n;
    while(n--)
    {   cin>>a>>b;
        s=change(a)+change(b);
        cout<<change(s)<<endl;
    }
return 0;
}