[Codility] Lession 5.1 Passing cars

Test URL can be found in extension link
Swift solution:

public func solution (inout A: [Int]) -> Int {
    var multiply = 0
    var passings = 0
    for car in A {
        // If the car is 0, means the car is driving EAST
        if (car == 0) { multiply += 1 }
       // Ignore those cars (to WEST) before you find the first car (to EAST)
        if (multiply > 0) {
            
       // If you already found some car (to EAST)
       // and if the current car is the car (to WEST)
       // then this car will pass them eventually.
            if car == 1 {
                passings += multiply
            
// If passing count more than certain number,shall return -1 
// as the question expected
                if passings > 1000000000{ return -1 }
            }
        }
    }
    return passings
}