Swift generic binary search

binarySearch

// Binary search

func binarySearch<T: Comparable>(target: T, collection: [T]) -> Int {

    var min = 0
    var max = countElements(collection) - 1

    return binaryMakeGuess(min, max, target, collection)

}


func binaryMakeGuess<T: Comparable>(min: Int, max: Int, target: T, collection: [T]) -> Int {

    let guess = (min + max) / 2

    if max < min {

        // illegal, guess not in array
        return -1

    } else if collection[guess] == target {

        // guess is correct
        return guess

    } else if collection[guess] > target {

        // guess is too high
        return binaryMakeGuess(min, guess - 1, target, collection)

    } else {

        // array[guess] < target
        // guess is too low
        return binaryMakeGuess(guess + 1, max, target, collection)

    }
}



let strings = ["a", "b", "c", "d", "e", "f"]
binarySearch("a", strings)
binarySearch("z", strings)

let nums = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
binarySearch(7, nums)
binarySearch(-2, nums)