Beat the Spread!

FJNU.1250

Description
Superbowl Sunday is nearly here. In order to pass the time waiting for the half-time commercials and wardrobe malfunctions, the local hackers have organized a betting pool on the game. Members place their bets on the sum of the two final scores, or on the absolute difference between the two scores.
Given the winning numbers for each type of bet, can you deduce the final scores?

Input
The first line of input contains n, the number of test cases. n lines follow, each representing a test case. Each test case gives s and d, non-negative integers representing the sum and (absolute) difference between the two final scores.

Output
For each test case, output a line giving the two final scores, largest first. If there are no such scores, output a line containing "impossible". Recall that football scores are always non-negative integers.

Sample Input
2
40 20
20 40

Sample Output
30 10
impossible

Source
5 February, 2005 - Waterloo local contest

My Program

#include<stdio.h>
int main()
...{
  int i,n,s[500],d[500];
  scanf("%d",&n);
  for(i=0;i<n;i++)
    scanf("%d%d",&s[i],&d[i]);
  for(i=0;i<n;i++)
    if((s[i]-d[i])<0) printf("impossible ");
    else if((s[i]-d[i])%2!=0) printf("impossible ");
    else printf("%d %d ",(s[i]+d[i])/2,(s[i]-d[i])/2);
  return 0;
}

YOYO‘s Note:
只是判断两数大小及是否相差偶数而已……
当时还不知道边输入边输出，足足开了500的数组 = = 好浪费……