Merge-Sort Algorithm

merge-sort.py

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+# This is an implementation of the merge sort algorithm in Python,
+# which is a divide-and-conquer algorithm that splits a given array into two halves,
+# sorts them, and then merges them together
+
+# This script is well docummented with comments to explain every step of this proccess
+
+def merge_sort(array):
+    # Returns 1 if the array contains none or just a single number
+    if len(array) <= 1:
+        return
+
+    # Calculate the middle index of the array and split it in two halves
+    middle_point = len(array) // 2
+    left_part = array[:middle_point]
+    right_part = array[middle_point:]
+
+    # Recursive call to the merge_sort function
+    merge_sort(left_part)
+    merge_sort(right_part)
+
+    # These variables will be used to iterate through the halves and merge them together
+    left_array_index = 0
+    right_array_index = 0
+    sorted_index = 0
+
+    # Iterates through both halves and compares their elements
+    while left_array_index < len(left_part) and right_array_index < len(right_part):
+        # If the left element is smaller, it is placed in the sorted position in the original array,
+        # and the left_array_index is incremented
+        if left_part[left_array_index] < right_part[right_array_index]:
+            array[sorted_index] = left_part[left_array_index]
+            left_array_index += 1
+        # If the right element is smaller, it is placed in the sorted position in the original array,
+        # and the right_array_index is incremented
+        else:
+            array[sorted_index] = right_part[right_array_index]
+            right_array_index += 1
+        sorted_index += 1
+        # The sorted_index is incremented after placing an element in the sorted position
+
+    # For the left half:
+    # Place the remaining elements in the sorted position in the original array
+    # and increment the indices
+    while left_array_index < len(left_part):
+        array[sorted_index] = left_part[left_array_index]
+        left_array_index += 1
+        sorted_index += 1
+
+    # For the right half:
+    # Place the remaining elements in the sorted position in the original array
+    # and increment the indices
+    while right_array_index < len(right_part):
+        array[sorted_index] = right_part[right_array_index]
+        right_array_index += 1
+        sorted_index += 1
+
+
+# Checks if the script is being run directly or imported as a module
+if __name__ == '__main__':
+
+    # Define an unsorted array and print it
+    numbers = [4, 10, 6, 14, 2, 1, 8, 5]
+    print('Unsorted array:',numbers)
+
+    # Call the merge_sort function on the unsorted array and print the sorted array
+    merge_sort(numbers)
+    print('Sorted array:',str(numbers))