swapTwoInts.swift

func swapTwoIntsWithInout(a: inout Int, b: inout Int) {
    let temporaryA = a
    a = b
    b = temporaryA
}


var firstNumber = 10
var secondNumber = 30

print("firstNumber : \(firstNumber)")       // 10
print("secondNumber : \(secondNumber)")     // 30

swapTwoIntsWithInout(a: &firstNumber, b: &secondNumber)

print("firstNumber : \(firstNumber)")       // 30
print("secondNumber : \(secondNumber)")     // 10