# bubble sort: make repeated passes through the list,
# moving the greatest number to the end; each time through,
# the length of the list sorted shrinks by 1 (because the
# end of the list is sorted)
#
# we print the current state of the list each time through
#
# also count (and print) the number of comparisons and
# exchanges
# 
# Matt Bishop   ECS 36A, Winter 2019
#

#
# set this to False to print *only* the original (unsorted)
# and the final (sorted) lists
# set to True to print the intermediate (partially sorted) lists
#
showintermediate = True

#
# we will generate a list of this many numbers
# and then shuffle them 7 times using shuffle()
# from the random module
#
import random
nnums = 20

# set the number of swaps and comparisons to 0
swaps = 0
compares = 0

#
# this is the bubble sort routine
# 
def bubblesort(numlist):
        # we track the number of comparisons and swaps (exchanges)
        global swaps, compares
        # get length of list
        n = len(numlist)
        # initially we assume something has to be swapped
        swapped = True

        # continue looping until no numbers are swapped
        while swapped:
                # print the current state of the list (visually see the sorting)
                if showintermediate:
                        print("         ", numlist)
                # okay, no swaps on this pass -- yet
                swapped = False
                # go through the list, moving the highest number to the end
                # you swap the numbers in pairs, hence the "bubbling"
                for i in range(1, n):
                        # another comparison
                        compares += 1
                        # if true, the greater number is first, so we
                        # need to exchange the numbers to move the greater
                        # one closer to the end
                        if numlist[i-1] > numlist[i]:
                                # a swap will occur
                                swaps += 1
                                swapped = True
                                # and here is the swap
                                numlist[i-1], numlist[i] = numlist[i], numlist[i-1]

#
# generate a list of numbers
# we just put the first nnums number into a list (0 .. nnums-1)
# and then shuffle it 7 times
#
def loadnums():
        # generate the list; use range and convert it
        numlist = list(range(nnums))

        # now shuffle 7 times; in theory, this makes
        # it as random as possible
        for i in range(0, 7):
                random.shuffle(numlist)
                
        # and return the list!
        return numlist

#
# this puts it all together
#
def main():
        # we need to print these
        global compares, swaps
        
        # get the list
        # if it's empty, quit (just in case :)
        nums = loadnums()
        if nums == []:
                return

        # print the initial list
        print("Unsorted:", nums)
        
        # sort the list
        bubblesort(nums)

        # print the sorted list and the relevant statistics
        print("  Sorted:", nums)
        print("This took {} comparisons and {} swaps".format(compares, swaps))

#
# and we're off!
#
main()