ChristmasTree.swift

ChristmasTree.swift

extension BinaryInteger {
    func printPyramid() {
        guard self > 0 else { return }
        for i in 0...up {
//            let offset = i <= 9 ? "0" : ""
            let spaceStr = Array(repeating: " ", count: up - i).joined()
            let numsStr = Array(0...i).toString
//            let numsStr =  Array(repeating: "\(offset)\(i.specStringInternal)", count: i).joined()
            print(spaceStr + numsStr)
        }
    }
}

extension Collection where Element: BinaryInteger {
    var toString: String {
        return self.map { "\($0) " }.joined()
    }
}

extension BinaryInteger {
    private var up: Int { return Int(self) }
    
    private var powerOfTen: Int { return "\(self)".count - 1 }
    
    private var toInt: Int { return Int(self) }
    
    private var specStringInternal: String {
        return "\(self) " + Array(repeating: " ", count: (up - self.toInt).powerOfTen).joined()
    }
}

//: ## Usage
30.printPyramid()