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  • 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();
    	}
    }
    
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  • 原文地址:https://www.cnblogs.com/tonyluis/p/4579097.html
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