Stack: Implement Stack Using Queues

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 empty operations 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).

Update (2015-06-11):

The class name of the Java function had been updated to MyStack instead of Stack.

Credits:

Special thanks to @jianchao.li.fighter for adding this problem and all test cases.

class MyStack { Queue<Integer> q = new LinkedList<Integer>(); // Push element x onto stack. public void push(int x) { q.add(x); for(int i = 0; i < q.size()-1 ;i++){ q.add(q.remove()); } } // Removes the element on top of the stack. public void pop() { q.remove(); } // Get the top element. public int top() { return q.peek(); } // Return whether the stack is empty. public boolean empty() { return q.isEmpty(); } }