Cocktail Sort #198

[bandaabhigna]

def cocktailSort(a):
n = len(a)
swapped = True
start = 0
end = n-1
while (swapped == True):

    # reset the swapped flag on entering the loop, 
    # because it might be true from a previous 
    # iteration. 
    swapped = False

    # loop from left to right same as the bubble 
    # sort 
    for i in range (start, end): 
        if (a[i] > a[i + 1]) : 
            a[i], a[i + 1]= a[i + 1], a[i] 
            swapped = True

    # if nothing moved, then array is sorted. 
    if (swapped == False): 
        break

    # otherwise, reset the swapped flag so that it 
    # can be used in the next stage 
    swapped = False

    # move the end point back by one, because 
    # item at the end is in its rightful spot 
    end = end-1

    # from right to left, doing the same 
    # comparison as in the previous stage 
    for i in range(end-1, start-1, -1): 
        if (a[i] > a[i + 1]): 
            a[i], a[i + 1] = a[i + 1], a[i] 
            swapped = True

    # increase the starting point, because 
    # the last stage would have moved the next 
    # smallest number to its rightful spot. 
    start = start + 1