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
<?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);
?>