Akande Joshua

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# HackerRank: Diagonal Difference Solution using PHP (Algorithm)

## 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);
}
``````