"""
A pure Python implementation of the insertion sort algorithm
This algorithm sorts a collection by comparing adjacent elements.
When it finds that order is not respected, it moves the element compared
backward until the order is correct. It then goes back directly to the
element's initial position resuming forward comparison.
For doctests run following command:
python3 -m doctest -v insertion_sort.py
For manual testing run:
python3 insertion_sort.py
"""
from collections.abc import MutableSequence
from typing import Any, Protocol, TypeVar
class Comparable(Protocol):
def __lt__(self, other: Any, /) -> bool: ...
T = TypeVar("T", bound=Comparable)
def insertion_sort(collection: MutableSequence[T]) -> MutableSequence[T]:
"""A pure Python implementation of the insertion sort algorithm
:param collection: some mutable ordered collection with heterogeneous
comparable items inside
:return: the same collection ordered by ascending
Examples:
>>> insertion_sort([0, 5, 3, 2, 2])
[0, 2, 2, 3, 5]
>>> insertion_sort([]) == sorted([])
True
>>> insertion_sort([-2, -5, -45]) == sorted([-2, -5, -45])
True
>>> insertion_sort(['d', 'a', 'b', 'e', 'c']) == sorted(['d', 'a', 'b', 'e', 'c'])
True
>>> import random
>>> collection = random.sample(range(-50, 50), 100)
>>> insertion_sort(collection) == sorted(collection)
True
>>> import string
>>> collection = random.choices(string.ascii_letters + string.digits, k=100)
>>> insertion_sort(collection) == sorted(collection)
True
"""
for insert_index in range(1, len(collection)):
insert_value = collection[insert_index]
while insert_index > 0 and insert_value < collection[insert_index - 1]:
collection[insert_index] = collection[insert_index - 1]
insert_index -= 1
collection[insert_index] = insert_value
return collection
if __name__ == "__main__":
from doctest import testmod
testmod()
user_input = input("Enter numbers separated by a comma:\n").strip()
unsorted = [int(item) for item in user_input.split(",")]
print(f"{insertion_sort(unsorted) = }")
Given an array of n elements, write a function to sort the array in increasing order.
О(n^2)
comparisons, О(n^2)
swaps -- Worst Case
O(n)
comparisons, O(1)
swaps -- Best Case
O(1)
-- (No extra space needed, sorting done in place)
12, 11, 13, 5, 6
Let us loop for i = 1 (second element of the array) to 4 (Size of input array)
i = 1.
Since 11 is smaller than 12, move 12 and insert 11 before 12
11, 12, 13, 5, 6
i = 2.
13 will remain at its position as all elements in sorted subarray are smaller than 13
11, 12, 13, 5, 6
i = 3.
5 will move to the beginning,
and all other elements from 11 to 13 will move one position ahead of their current position.
5, 11, 12, 13, 6
i = 4.
6 will move to position after 5,
and elements from 11 to 13 will move one position ahead of their current position.
5, 6, 11, 12, 13 -- sorted array