Shift all zeros in array to the right most indexes in linear time.

ShiftZerosInArray.swift

func shiftZeros(in array: inout [Int]) {
    var indexToPlaceZero = array.count - 1
    for i in array.indices {
        if array[i] == 0 {
            while array[indexToPlaceZero] == 0, i < indexToPlaceZero {
                indexToPlaceZero -= 1
            }
            array.swapAt(i, indexToPlaceZero)
        }
    }
}