def bubble_sort(L):
    '''Sort the items in L in non-descending order.'''
    for i in range(0, len(L)):
        for j in range(0, len(L) - i - 1):
            if L[j] > L[j + 1]:
                L[j], L[j + 1] = L[j + 1], L[j]
    return L

def find_min(L, i):
    '''Return the index of the smallest item in L[i:]'''
    smallest = i # The index of the smallest so far
    for j in range(i + 1, len(L)):
        if L[j] < L[smallest]:
            smallest = j
    return smallest

def selection_sort(L):
    '''Sort the items in L in non-descending order.'''
    i = 0
    # L[:i] is sorted.
    while i < len(L):
        smallest = find_min(L, i)
        #swap
        temp = L[smallest]
        L[smallest] = L[i]
        L[i] = temp
        i += 1
    return L

def selection_sort2(L):
    '''Sort the items in L in non-descending order.'''
    for i in range(len(L)):
        smallest = find_min(L, i)
        L[smallest], L[i] = L[i], L[smallest]
    return L

def insert(L, i):
    '''Move L[i] to where it belongs in L[:i].'''
    v = L[i]
    while i > 0 and L[i - 1] > v:
        L[i] = L[i - 1]
        i -= 1
    L[i] = v

def insertion_sort(L):
    '''Sort the items in L in non-descending order.'''
    i = 0
    # L[:i] is sorted.
    while i != len(L):
        insert(L, i)
        i += 1
    return L

def insertion_sort2(L):
    '''Sort the items in L in non-descending order.'''
    for i in range(len(L)):
        insert(L, i)
    return L

def merge(left, right):
    '''Return the list made by merging sorted lists left and right.'''
    result = []
    i ,j = 0, 0
    while i < len(left) and j < len(right):
        if left[i] <= right[j]:
            result.append(left[i])
            i = i + 1
        else:
            result.append(right[j])
            j = j + 1

    # One of the sublists has elements left over; the other is empty. Copying
    # both makes sure we get it.
    result += left[i:]
    result += right[j:]
    return result
    
def merge_sort(L):
    '''Sort the items in L in non-descending order.'''
    if len(L) < 2:
        return L
    else:
        middle = len(L) / 2
        left = merge_sort(L[:middle])
        right = merge_sort(L[middle:])
        return merge(left, right)

selection_sort([1,3,56,54,3,8,2,33])