Swift Xcode implementation of InterviewCake _Product of integers in an array_ using an `Array` extension. ⚠️ Spoiler alert: this is an actual answer to the https://www.interviewcake.com/question/swift/product-of-other-numbers question, so no peeking!

InterviewCake-Array+ProductsOfAllIntsExceptAdIndex.swift

//
//  Array+ProductsOfAllIntsExceptAdIndex.swift
//
//  Copyright © 2018 Xavier Schott
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.
//

import Foundation

extension Array where Element == Int {
    func getProductsOfAllIntsExceptAtIndex() -> [Double] {

        var result = [Double](repeatElement(0, count: count))
        var cumul:Double = 1
        for i in (0 ..< count).reversed() {
            result[i] = cumul
            cumul *= Double(self[i])
        }

        cumul = 1
        for i in 0 ..< count {
            result[i] *= cumul
            cumul *= Double(self[i])
        }
        return result
    }
}

InterviewCake-ProductOfIntegersTests.swift

//
//  ProductOfIntegersTests.swift
//
//  Copyright © 2018 Xavier Schott
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.

//

import XCTest

class ProductOfIntegersTests: XCTestCase {    
    func test1734() {
        let array = [1, 7, 3, 4]
        let expected:[Double] = [84, 12, 28, 21]
        let result = array.getProductsOfAllIntsExceptAtIndex()
        XCTAssertEqual(expected, result, "\(array) != \(result)")
    }

    func test17340() {
        let array = [1, 7, 3, 4, 0]
        let expected:[Double] = [0, 0, 0, 0, 84]
        let result = array.getProductsOfAllIntsExceptAtIndex()
        XCTAssertEqual(expected, result, "\(array) != \(result)")
    }

    func testGetProductsOfAllIntsExceptAtIndex() {
        var largeArray = [Int](repeatElement(0, count: 16384))
        for i in 0 ..< largeArray.count {
            largeArray[i] = 1 + Int(arc4random_uniform(2))
        }
        self.measure { // Time 0.0012 sec
            _ = largeArray.getProductsOfAllIntsExceptAtIndex()
        }
    }
}