Java for LeetCode 225 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.

解题思路：

用Queue的实例LinkedList实现，JAVA实现如下：

class MyStack {
	LinkedList<Integer> queue;

	MyStack() {
		this.queue = new LinkedList<Integer>();
	}

	// Push element x onto stack.
	public void push(int x) {
		queue.add(x);
	}

	// Removes the element on top of the stack.
	public void pop() {
		queue.remove(queue.size()-1);
	}

	// Get the top element.
	public int top() {
		return queue.getLast();
	}

	// Return whether the stack is empty.
	public boolean empty() {
		return queue.isEmpty();
	}
}