2020-03-01

Author: JiayangWu

0225.用队列实现栈/0225-用队列实现栈.py

@@ -1,53 +1,44 @@
+from collections import deque
 class MyStack(object):
-
     def __init__(self):
         """
         Initialize your data structure here.
         """
-        self.queue1 = []
-        self.queue2 = []
+        self.q1 = deque()
+        self.q2 = deque()
 
     def push(self, x):
         """
         Push element x onto stack.
         :type x: int
         :rtype: None
         """
-        self.queue1.append(x)
-
-        while len(self.queue1) > 1:
-            self.queue2.append(self.queue1[0])
-            self.queue1 = self.queue1[1:]
+        self.q1.append(x)
+        while self.q2:
+            self.q1.append(self.q2.popleft())
+        self.q2 = self.q1
+        self.q1 = deque()
 
-            
-        # print self.queue1, self.queue2
     def pop(self):
         """
         Removes the element on top of the stack and returns that element.
         :rtype: int
         """
-        # print self.queue1, self.queue2
-        top = self.queue1[0]
-        self.queue1, self.queue2 = self.queue2, []
-        while len(self.queue1) > 1:
-            self.queue2.append(self.queue1[0])
-            self.queue1 = self.queue1[1:]
-        return top
-            
+        return self.q2.popleft()
 
     def top(self):
         """
         Get the top element.
         :rtype: int
         """
-        return self.queue1[0]
-        
+        return self.q2[0]
+
     def empty(self):
         """
         Returns whether the stack is empty.
         :rtype: bool
         """
-        return not self.queue1 and not self.queue2
+        return not self.q2
 
 
 # Your MyStack object will be instantiated and called as such: