Quiz 32: Find symmetric point

Problem:

Given two points, find the symmetric point (C is symmetric point of A and B, if B is mid point of A and C)

Input Format: 

first line, T, contains number of test cases

T lines contains coordinates of 2 points A and B

Output Format: 
Each line, containing symmetric point of A and B

Constraints: 
none

Sample Input

2
0 0 2 2
1 1 3 3

Sample Output:
4 4
5 5

Explanations:
for first test case, 2,2 is midpoint of 4,4 and 0,0

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Solution:

@out=();
chomp($t=<STDIN>);
for($i=0;$i<$t;$i++)
    {
    chomp($c=<STDIN>);
    @arr=split(" ",$c);
    $a=(2*$arr[2])-$arr[0];
    $b=(2*$arr[3])-$arr[1];
    push(@out,$a);
    push(@out,$b);
    }
$len=@out;
for($j=0;$j<$len;$j++)
    {
    print "$out[$j] $out[$j+1]\n";
    $j++;
    }

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Tips:

Simple, C= 2B-1