Add doctests for sorting algorithms (#1263)

* doctests and intro docstring added

* doctests, docstrings and check for empty collection added

* Intro docstring added

* python versions reversed

sorts/pancake_sort.py

@@ -1,9 +1,25 @@
-"""Pancake Sort Algorithm."""
-# Only can reverse array from 0 to i
-
+"""
+This is a pure python implementation of the pancake sort algorithm
+For doctests run following command:
+python3 -m doctest -v pancake_sort.py
+or
+python -m doctest -v pancake_sort.py
+For manual testing run:
+python pancake_sort.py
+"""
 
 def pancake_sort(arr):
-    """Sort Array with Pancake Sort."""
+    """Sort Array with Pancake Sort.
+    :param arr: Collection containing comparable items
+    :return: Collection ordered in ascending order of items
+    Examples:
+    >>> pancake_sort([0, 5, 3, 2, 2])
+    [0, 2, 2, 3, 5]
+    >>> pancake_sort([])
+    []
+    >>> pancake_sort([-2, -5, -45])
+    [-45, -5, -2]
+    """
     cur = len(arr)
     while cur > 1:
         # Find the maximum number in arr
@@ -17,4 +33,6 @@ def pancake_sort(arr):
 
 
 if __name__ == '__main__':
-    print(pancake_sort([0, 10, 15, 3, 2, 9, 14, 13]))
+    user_input = input('Enter numbers separated by a comma:\n').strip()
+    unsorted = [int(item) for item in user_input.split(',')]
+    print(pancake_sort(unsorted))

sorts/pigeon_sort.py

@@ -1,7 +1,29 @@
 '''
     This is an implementation of Pigeon Hole Sort.
+    For doctests run following command:
+    
+    python3 -m doctest -v pigeon_sort.py
+    or
+    python -m doctest -v pigeon_sort.py
+    
+    For manual testing run:
+    python pigeon_sort.py
 '''
 def pigeon_sort(array):
+    """
+    Implementation of pigeon hole sort algorithm
+    :param array: Collection of comparable items
+    :return: Collection sorted in ascending order
+    >>> pigeon_sort([0, 5, 3, 2, 2])
+    [0, 2, 2, 3, 5]
+    >>> pigeon_sort([])
+    []
+    >>> pigeon_sort([-2, -5, -45])
+    [-45, -5, -2]
+    """
+    if(len(array) == 0):
+        return array
+
     # Manually finds the minimum and maximum of the array.
     min = array[0]
     max = array[0]
@@ -37,6 +59,4 @@ def pigeon_sort(array):
 if __name__ == '__main__':
     user_input = input('Enter numbers separated by comma:\n')
     unsorted = [int(x) for x in user_input.split(',')]
-    sorted = pigeon_sort(unsorted)
-
-    print(sorted)
+    print(pigeon_sort(unsorted))