Find the count of given number in a sorted array.

count.py

def count(array, n):
    
    # starting point
    left, right = 0, len(array)
    while left < right:
        mid = (left + right) / 2
        if array[mid] >= n:
            right = mid
        else:
            left = mid + 1
    # before exiting the loop, right points
    # to the given number if any:
    # array[right] >= n
    start = right
    
    # ending point
    left, right = 0, len(array)
    while left < right:
        mid = (left + right) / 2
        if array[mid] <= n:
            left = mid + 1
        else:
            right = mid
    # before exiting the loop, left points
    # to the immediate right of given number
    # if any: array[left - 1] <= n
    end = left
    
    return end - start