Difference between sums of two diagonals of a square matrix

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

The most efficient way is to approach this is to implement a solution running linearly achieving the 0(n).

We will create a method sumOfDiagonals which takes in a parameter arr: Array<IntArray>. This allows us to create a 2D array. Create variables leftToRight, rightToLeft which will be equal to 0 representing the diagonal lines. Variable rows equal to the size of the array arr.size and columns equal to the size of the positions arr[0].size.

Create the counters for the positions and assert them to 0. var i = 0, var j = 0, var k = 0, var l = arr.size - 1 this a right to left column counter.

Create a while loop that checks the rows and column counters and if the value is satisfied it should increment the counters and add the leftToRight, rightToLeft values together.

To make it work return the absolute difference return Math.abs(leftToRight - rightToLeft).

Easy Peasy, Lemon Squeezy 😄 😄.

Let's look at the code

fun sumOfDiagonals(arr: Array<IntArray>): Int {

    var leftToRight = 0
    var rightToLeft = 0
    val rows = arr.size
    val columns = arr[0].size

    var i = 0
    var j = 0
    var k = 0
    var l = arr.size - 1 //right to left column counter

    while (rows >= 0 && columns >= 0 && rows >= 0 && l >= 0) {

        leftToRight += arr[i][j] //add the values at the position
        rightToLeft += arr[k][l] //add the values at the position

        i += 1
        j += 1
        k += 1
        l -= 1

    }

    return abs(leftToRight - rightToLeft) ///return the difference

}

Github Repo

Thank you for reading, please share if you found it helpful 💯.

Asante Sana