封装成函数更简洁一点 

#include <stdio.h>
#include <math.h>

int main(){
    int n1,t1,t2,n2;
    while(scanf("%d %d",&n1,&n2)!=EOF){
        int sum1=0,sum2=0,len1=0,len2=0;
        t1 = n1;
        t2 = n2;
        while(t1>0){
            t1 /= 10;
            len1++;
        }
        while(n1>0){
            sum1 = sum1 + n1%10*pow(10, len1-1);
            n1 /= 10;
            len1--;
        }
        
        while(t2>0){
            t2 /= 10;
            len2++;
        }
        while(n2>0){
            sum2 = sum2 + n2%10*pow(10, len2-1);
            n2 /= 10;
            len2--;
        }
        printf("%d\n",sum1+sum2);
    }
    return 0;
}