Implement Stack using Queues

Description:

Implement the following operations of a stack using queues.

• push(x) -- Push element x onto stack.
• pop() -- Removes the element on top of the stack.
• top() -- Get the top element.
• empty() -- Return whether the stack is empty.

Notes:

• You must use only standard operations of a queue -- which means only push to back, peek/pop from front, size, and is emptyoperations are valid.
• Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
• You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

Code:

 1 class Stack {
 2 public:
 3     // Push element x onto stack.
 4     void push(int x) {
 5         m.push_front(x);
 6     }
 7 
 8     // Removes the element on top of the stack.
 9     void pop() {
10         if (!m.empty())
11             m.pop_front(); 
12     }
13 
14     // Get the top element.
15     int top() {
16         if (!m.empty())
17             return m.front();
18     }
19 
20     // Return whether the stack is empty.
21     bool empty() {
22        if (m.size()==0)
23         return true;
24        else
25         return false;
26     }
27     private:
28     deque<int>m;
29 };

View Code

Implement Stack using Queues

原文：http://www.cnblogs.com/happygirl-zjj/p/4598850.html