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3-quick-sort-count-pivots.py
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3-quick-sort-count-pivots.py
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def generate_median(array, left_index, right_index):
middle_index = 0 if right_index - left_index == 1 else (right_index - left_index) // 2 + left_index
left = array[left_index]
right = array[right_index]
middle = array[middle_index]
candidates = sorted([(left, left_index), (middle, middle_index), (right, right_index)])
return candidates[1][1]
def choose_pivot(array, choice, left, right):
if choice == 1:
return left
elif choice == 2:
return right
else:
return generate_median(array, left, right)
def partition(array, choice, left, right):
global count
i = choose_pivot(array, choice, left, right)
pivot = array[i]
array[left], array[i] = array[i], array[left]
i = left + 1
for j in range(i, right + 1):
count += 1
if array[j] < pivot:
array[i], array[j] = array[j], array[i]
i += 1
i -= 1
array[i], array[left] = array[left], array[i]
return i
def count_quick_sort(array, choice, left, right):
if len(array) < 1:
return
if left <= right:
pivot = partition(array, choice, left, right)
count_quick_sort(array, choice, left, pivot - 1)
count_quick_sort(array, choice, pivot + 1, right)
file = open("D:\\Algorithms-Specialization\\files\\quick_sort_integers.txt")
lines = file.readlines()
file.close()
num_array = []
for n in range(0, len(lines)):
lines[n] = lines[n].strip()
num_array.append(int(lines[n]))
count = 0
choice = int(input("input your choice of pivot (1: Leftmost, 2: Rightmost, 3: Median): "))
count_quick_sort(num_array, choice, 0, len(num_array) - 1)
print(num_array)
print(count)