merge sort python

merge_sort/merge-sort.py

@@ -0,0 +1,29 @@
+def merge(s1, s2, s):
+    i = j = 0
+
+    while i + j < len(s):
+        if j == len(s2) or (i < len(s1) and s1[i] < s2[j]):
+            s[i+j] = s1[i]              # ith of S1 as next item of S
+            i += 1
+        else:
+            s[i+j] = s2[j]              # jth of S2 as next item of S
+            j += 1
+
+def merge_sort(s):
+    n = len(s)
+    if n<2:
+        return              # already sorted
+    # divide
+    mid = n //2
+    s1 = s[0:mid]
+    s2 = s[mid:n]
+    # conquer  - recursive
+    merge_sort(s1)
+    merge_sort(s2)
+
+    merge(s1,s2,s)          # merge halfs back to s
+
+array = [5,6,2,4,3,1,0,0]
+print("before:", array)
+merge_sort(array)
+print("sorted:", array)