(hdu簡単問題128題)hdu 1194 Beat the Spread!(既知の2つの数とuの2つの数の差はこの2つの数を求める)

タイトル:
Beat the Spread!
Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 5169    Accepted Submission(s): 2692
Problem 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
University of Waterloo Local Contest 2005.02.05
 
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テーマ分析:
               a+bとa-bはa、bを求めることが知られている.
コードは次のとおりです.

/*
 * b.cpp
 *
 *  Created on: 2015 3 12 
 *      Author: Administrator
 */

#include <iostream>
#include <cstdio>

using namespace std;


int main(){
	int t;
	scanf("%d",&t);
	while(t--){
		int sum;
		int diff;
		scanf("%d%d",&sum,&diff);

		if(sum < diff){//       <     
			printf("impossible
");//      (a,b >=0)
		}else if((sum+diff)%2 != 0){//  (a+b) + (a-b)     
			printf("impossible
");//   
		}else{//        
			printf("%d %d
",(sum+diff)/2,(sum-diff)/2);//          
		}
	}

	return 0;
}