import UIKit

func countOccurance<T: Comparable>(array: [T], searchValue: T) -> Int {

    func rightBoundary() -> Int {
        var lowerBound = 0
        var upperBound = array.count

        while lowerBound < upperBound {
            let midPoint = lowerBound + (upperBound-lowerBound)/2
            if searchValue < array[midPoint] {
                upperBound = midPoint
            } else {
                lowerBound = midPoint + 1
            }
        }
        return lowerBound
    }

    func leftBoundary() -> Int {
        var lowerBound = 0
        var upperBound = array.count

        while lowerBound < upperBound {
            let midPoint = lowerBound + (upperBound-lowerBound)/2
            if searchValue > array[midPoint] {
                lowerBound = midPoint + 1
            } else {
                upperBound = midPoint
            }
        }
        return lowerBound
    }
    return rightBoundary() - leftBoundary()
}

let numbers = [2,3,4,6,7,8,10]
let value = countOccurance(array: numbers, searchValue: 5)