def partition(lst, start, end):
middle_value = lst[end]
middle_index = start - 1
for index in range(start, end):
if lst[index] <= middle_value:
middle_index += 1
swap(lst, middle_index, index)
middle_index += 1
swap(lst, middle_index, end)
return middle_index
def partition(lst, median_value):
"""divide lst by median_value and return the index of median_value"""
middle_index = -1
for i in range(len(lst)):
if lst[i] <= median_value:
middle_index += 1
swap(lst, middle_index, i)
if lst[middle_index] == median_value:
self_index = middle_index
swap(lst, middle_index, self_index)
return middle_index
def radix_sort(lst):
"""sorting a word list to dict-order"""
# get the length of the longest word
longest_length = 0
if len(lst) < 0:
return
for i in range(len(lst)):
if len(lst[i]) > longest_length:
longest_length = len(lst[i])
# sorting
for i in range(longest_length - 1, -1, -1):
# using any stable sorting algo, for example bubble sort
for x in range(1, len(lst)):
for y in range(len(lst) - x):
if get_alphabet(lst, y) > get_alphabet(lst, y + 1):
swap(lst, y, y + 1)
def quick_sort(lst, start=0, end=-1):
if end == -1:
end = len(lst) - 1
if start < end:
exchange_index = start - 1
# randomized middle value
middle_index = np.random.randint(start, end)
swap(lst, middle_index, end)
for i in range(start, end):
if lst[i] <= lst[end]:
exchange_index += 1
swap(lst, i, exchange_index)
exchange_index += 1
swap(lst, end, exchange_index)
if start < exchange_index:
quick_sort(lst, start, exchange_index-1)
if exchange_index < end:
quick_sort(lst, exchange_index+1, end)
def randomized_partition(lst, start, end):
middle = np.random.randint(start, end)
swap(lst, middle, end)
return partition(lst, start, end)