Fix stack behaving as a queue as per course video

Author: jslvtr

course_contents/21_algorithms_data_structures/projects/samples/stack.py

@@ -3,10 +3,10 @@ def __init__(self):
         self.items = []
 
     def push(self, e):
-        self.items.append(e)
+        self.items = [e] + self.items
 
     def pop(self):
-        return self.items.pop()
+        return self.items.pop(0)
 
 
 s = Stack()