Diagonal Difference.swift

/**
 * @author: syed ashraf ullah
 * date: 07/2019
 * problem: https://www.hackerrank.com/challenges/diagonal-difference/problem
 */
 import Foundation

/*
 * Complete the 'diagonalDifference' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts 2D_INTEGER_ARRAY arr as parameter.
 */

func diagonalDifference(arr: [[Int]]) -> Int {
    // Write your code here

    var size: Int = arr.count
    var diagonalSum:[Int] = [0,0]
    size -= 1
    for item in 0...size{
        diagonalSum[0] += arr[item][item]
        diagonalSum[1] += arr[item][size - item]
    }

    return abs(diagonalSum[0] - diagonalSum[1])

}

let stdout = ProcessInfo.processInfo.environment["OUTPUT_PATH"]!
FileManager.default.createFile(atPath: stdout, contents: nil, attributes: nil)
let fileHandle = FileHandle(forWritingAtPath: stdout)!

guard let n = Int((readLine()?.trimmingCharacters(in: .whitespacesAndNewlines))!)
else { fatalError("Bad input") }

var arr = [[Int]]()

for _ in 1...n {
    guard let arrRowTemp = readLine()?.replacingOccurrences(of: "\\s+$", with: "", options: .regularExpression) else { fatalError("Bad input") }

    let arrRow: [Int] = arrRowTemp.split(separator: " ").map {
        if let arrItem = Int($0) {
            return arrItem
        } else { fatalError("Bad input") }
    }

    guard arrRow.count == n else { fatalError("Bad input") }

    arr.append(arrRow)
}

guard arr.count == n else { fatalError("Bad input") }

let result = diagonalDifference(arr: arr)

fileHandle.write(String(result).data(using: .utf8)!)
fileHandle.write("\n".data(using: .utf8)!)