def bubbleSort(alist):
    for passnum in range(len(alist)-1,0,-1):
        for i in range(passnum):
            if alist[i]>alist[i+1]:
                #temp = alist[i]
                #alist[i] = alist[i+1]
                #alist[i+1] = temp
                alist[i],alist[i+1]=alist[i+1],alist[i]

def shortBubbleSort(alist):
    exchanges = True
    passnum = len(alist)-1
    while passnum > 0 and exchanges:
        exchangs = False
        for i in range(passnum):
            if alist[i]>alist[i+1]:
                exchanges = True
                temp = alist[i]
                alist[i] = alist[i+1]
                alist[i+1] = temp
        passnum = passnum - 1

def selectionSort(alist):
    for fillslot in range(len(alist)-1,0,-1):
        positionOfMax=0
        for location in range(1,fillslot+1):
            if alist[location]> alist[positionOfMax]:
                positionOfMax = location
        temp=alist[fillslot]
        alist[fillslot]=alist[positionOfMax]
        alist[positionOfMax]=temp

def insertionSort(alist):
    for index in range(1,len(alist)):
        currentvalue = alist[index]
        position = index
        while position>0 and alist[position-1]>currentvalue:
            alist[position]=alist[position-1]
            position=position-1
        alist[position]=currentvalue

def shellSort(alist):
    sublistcount = len(alist)//2
    print(sublistcount)
    while sublistcount > 0:
        for startposition in range(sublistcount):
            gapInsertionSort(alist,startposition,sublistcount)
        print("After increment of size",sublistcount,"The list is",alist)
        sublistcount = sublistcount // 2

def gapInsertionSort(alist,start,gap):
    for i in range(start+gap,len(alist),gap):
        currentvalue = alist[i]
        position = i
        while position >= gap and alist[position-gap] > currentvalue:
            alist[position]=alist[position-gap]
            position=position-gap
        alist[position]=currentvalue

def mergeSort(alist):
    print("Splitting ",alist)
    if len(alist)>1:
        mid = len(alist)//2
        lefthalf = alist[:mid]
        righthalf = alist[mid:]
        mergeSort(lefthalf)
        mergeSort(righthalf)
        i=0
        j=0
        k=0
        while i < len(lefthalf) and j < len(righthalf):
            if lefthalf[i] < righthalf[j]:
                alist[k]=lefthalf[i]
                i=i+1
            else:
                alist[k]=righthalf[j]
                j=j+1
            k=k+1
        while i < len(lefthalf):
            alist[k]=lefthalf[i]
            i=i+1
            k=k+1
        while j < len(righthalf):
            alist[k]=righthalf[j]
            j=j+1
            k=k+1
        print("Merging ",alist)

def quickSort(alist):
    quickSortHelper(alist,0,len(alist)-1)

def quickSortHelper(alist,first,last):
    if first<last:
        splitpoint = partition(alist,first,last)
        quickSortHelper(alist,first,splitpoint-1)
        quickSortHelper(alist,splitpoint+1,last)

def partition(alist,first,last):
    pivotvalue = alist[first]
    leftmark = first + 1
    rightmark = last
    done = False
    while not done:
        while leftmark <= rightmark and alist[leftmark] <= pivotvalue:
            leftmark = leftmark + 1
        while alist[rightmark] >= pivotvalue and rightmark >= leftmark:
            rightmark = rightmark - 1
        if rightmark < leftmark:
            done = True
        else:
            temp = alist[leftmark]
            alist[leftmark] = alist[rightmark]
            alist[rightmark] = temp
    temp = alist[first]
    alist[first] = alist[rightmark]
    alist[rightmark] = temp
    return rightmark

alist = [54,26,93,17,77,31,44,55,20]
quickSort(alist)
print(alist)