merge_sort merge_sort

Tp09/merge_sort.py

@@ -252,7 +252,13 @@ def mergesort(l: ApLst, comp: Callable[[T, T], int]=compare) -> ApLst:
     $$$ is_sorted(l1)
     True
     """
-    ...
+    if l.is_empty() or l.tail().is_empty():
+        return l
+    else:
+        l1, l2 = split(l)
+        sorted_l1 = mergesort(l1, comp)
+        sorted_l2 = mergesort(l2, comp)
+        return merge(sorted_l1, sorted_l2, comp)
 
 
 if (__name__ == '__main__'):