subtree(users/wpcarro): docking briefcase at '24f5a642'

git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c
git-subtree-split: 24f5a642af
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789

users/wpcarro/scratch/facebook/queue-two-stacks.py

@@ -0,0 +1,20 @@
+from stack import Stack
+
+class Queue(object):
+    def __init__(self):
+        self.lhs = Stack()
+        self.rhs = Stack()
+
+    def enqueue(self, x):
+        self.rhs.push(x)
+
+    def dequeue(self, x):
+        y = self.rhs.pop()
+        while y:
+            self.lhs.push(y)
+            y = self.rhs.pop()
+        result = self.lhs.pop()
+        y = self.lhs.pop()
+        while y:
+            self.rhs.push(y)
+        return result