20130707 【南华大学 ACM】 新生赛第一场 【A.Eming】

A.Eming

   

   Eming is a contest hold by WHUACM trainingteam. The aim is to select new members of the team.

   Usually, the first problem is a very simpleproblem such as “a+b problem”. But this time, Xioumu is tired of this kind of problem,he decide to solve “a and b problem”.

   Give you the result of a + b and a^2 – b^2,please output the result of a and b.

 

   Input

   There are several test cases. For each casethere are two double numbers indicating a+b and a^2-b^2. You may assume that a+bwill not be zero.

 

   Output

   For each case please output the result of aand b in one line, rounded to 2 decimal places.

 

   SampleInput

   3 -3

 

   SampleOutput

   1.00 2.00

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解题报告：

设 输入的 x,y 是（x=a+b,y=a^2-b^2）;

1)    y=a^2-b^2=(a-b)*(a+b)=(a-b)*x(x!=0)

2)    a-b=y/x

3)    a=(x+y/x)/2=x/2+y/2/x;

4)    b=x-a=(x-y/x)/2=x/2-y/2/x;

优化：

为减少运算次数，设xx=x/2;    yy=y/2/x;

则：a=xx+yy;    b=xx-yy;

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代码：

#include
int main()
{
    double x,y,xx,yy;
    while( EOF != scanf("%lf%lf",&x,&y) )
    {
        xx=x/2;
        yy=y/2/x;
        printf("%.2lf %.2lf\n",xx+yy,xx-yy);
    }
    return 0;
}