Case Study

Given a square matrix of size , calculate the absolute difference between the sums of its diagonals.

Input Format

The first line contains a single integer, . The next lines denote the matrix’s rows, with each line containing space-separated integers describing the columns.

Constraints

Output Format

Print the absolute difference between the two sums of the matrix’s diagonals as a single integer.

Sample Input

3
11 2 4
4 5 6
10 8 -12

Sample Output

15

Explanation

The primary diagonal is:

11
5
-12

Sum across the primary diagonal: 11 + 5 – 12 = 4

The secondary diagonal is:

4
5
10

Sum across the secondary diagonal: 4 + 5 + 10 = 19
Difference: |4 – 19| = 15

Note: |x| is absolute value function

Solution

Link to github

<?php

$handle = fopen ("php://stdin","r");
fscanf($handle,"%d",$n);
$a = array();
for($a_i = 0; $a_i < $n; $a_i++) {
 $a_temp = fgets($handle);
 $a[] = explode(" ",$a_temp);
 array_walk($a[$a_i],'intval');
}

$left=0;
$right=0;
$count= count($a);
for ($i=0; $i < $count; $i++) {
$left += $a[$i][$i];
$right += $a[$count-1-$i][$i];
}
echo abs($left - $right);

?>

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