Functional Pascal Triangle

pascalTriangle.swift

func makePascalTriangle(numOfRows: Int) -> ([[Int]]) {
    func getNextRow(_ arr: [Int]) -> [Int] {
        let a = zip([0]+arr, arr+[0])
        return a.map({
            (e: (Int, Int)) -> Int in
            e.0 + e.1
        })
    }
    
    func helper(_ countDown: Int, results: [[Int]]) -> (Int, [[Int]]) {
        if countDown == 0 {
            return (countDown, results)
        }
        let row = getNextRow(results.last!)
        return helper(countDown - 1, results: results + [row])
    }
    
    let initialPascal = [1]
    let (_, pascals) = helper(numOfRows, results: [initialPascal])
    return pascals
}

makePascalTriangle(numOfRows: 5)