Arrays: Left Rotation Swift 3.1 Cracking the Coding Interview

gistfile1.txt

// MARK : This is not very elegant solution, but working with input/output is really not nice on Swift 3.1
// so this just an example for working with input Sample Input like:
// 5 4
// 1 2 3 4 5
// in Arrays: Left Rotation (

import Foundation

func rotate(arr: [Int], offset: Int) -> [Int] {
    var newArray = [Int]()
    var newOffSet = offset
    if (newOffSet > arr.count) {
        newOffSet = offset % arr.count
    }
    
    for index in newOffSet...arr.count-1 {
          newArray.append(arr[index])
    }
    
    for index in 0...offset-1 {
        newArray.append(arr[index])
    }
    return newArray
}
// Read array with n elements with " " separated
var input = readLine()!.components(separatedBy: " ").map{ Int($0)! }
var n = input[0]
var d = input[1]
var arr =  readLine()!.components(separatedBy: " ").map{ Int($0)! }

for i in rotate(arr: arr, offset: d) {
    print(i, terminator: " ")
}

Swift 4 version ;)

extension Array {
    func rotateLeft(offset: Int) -> [Element] {
        let properOffset = offset % self.count
        let result = self[properOffset...] + self[..<properOffset]
        return Array(result)
    }
}

And a more generalized version that handles both right and left.. but this one is not that easy to read and it's not obvious which way the negative sign will rotate the array.

extension Array {
    func rotate(offset: Int) -> [Element] {
        let properOffset = offset % self.count
        let result: ArraySlice<Element>
        if properOffset > 0 {
            result = self[properOffset...] + self[..<properOffset]
        } else {
            let terminalOffset = count + properOffset
            result = self[(terminalOffset)...] + self[..<terminalOffset]
        }
        return Array(result)
    }
}