add merge sort

Author: Muh. Angga Muttaqien

sorting/merge-sort.py

@@ -0,0 +1,45 @@
+
+def merge_sort(collection):
+
+    length = len(collection)
+
+    if length > 1:
+        midpoint = length // 2
+        left_half = merge_sort(collection[:midpoint])
+        right_half = merge_sort(collection[midpoint:])
+        i = 0
+        j = 0
+        k = 0
+        left_length = len(left_half)
+        right_length = len(right_half)
+
+        while i < left_length and j < right_length:
+            if left_half[i] < right_half[j]:
+                collection[k] = left_half[i]
+                i += 1
+            else:
+                collection[k] = right_half[j]
+                j += 1
+            k += 1
+
+        while i < left_length:
+            collection[k] = left_half[i]
+            i += 1
+            k += 1
+
+        while j < right_length:
+            collection[k] = right_half[j]
+            j += 1
+            k += 1
+
+    return collection
+
+
+def main():
+    print("=== Merge Sort (Algorithm) - An efficient, general-purpose, comparison-based sorting algorithm which most implementations produce a stable sort. Merge-sort is a divide and conquer algorithm")
+    numbers = raw_input("Enter numbers separated by a comma: ")
+    unsorted = [int(item) for item in numbers.split(',')]
+    print(merge_sort(unsorted))
+
+if __name__=='__main__':
+	main()