## Diagonal Difference Solution

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

For example, the square matrix is shown below:

1 2 3

4 5 6

9 8 9

The left-to-right diagonal =1 + 5 + 9 = 15. The right to left diagonal = 3 + 5+ 9 = 17. Their absolute difference is **|15–17| = 2.**

**Function description**

Complete the diagonalDifference function in the editor below. It must return an integer representing the absolute diagonal difference.

**Difference takes the following parameter:**

arr: an array of integers.

**Input Format**

The first line contains a single integer, n , the number of rows and columns in the matrix arr.

Each of the next n lines describes a row, arr[i], and consists of n space-separated integers arr[i][j].

**Constraints**

. — 100 ≤ arr[i][j] ≤ 100

**Output Format**

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

**Sample Input**

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 the absolute value of x

## Solution (Base on how i solved it)

```
$first = 0;
$second = 0;
$n = sizeof($arr);
for ($i = 0; $i < $n; $i++){
for ($j = 0; $j < $n; $j++){
if ($i === $j){
$first += $arr[$i][$j];
}
if ($i + $j === $n - 1){
$second += $arr[$i][$j];
}
}
}
return abs($first - $second);
}
```

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