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ImplementStackUsingQueues.js
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// Source : https://leetcode.com/problems/implement-stack-using-queues/
// Author : Dean Shi
// Date : 2015-06-13
/**********************************************************************************
*
* 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.
*
**********************************************************************************/
/**
* @constructor
*/
var Stack = function() {
this.stack = [];
};
/**
* @param {number} x
* @returns {void}
*/
Stack.prototype.push = function(x) {
this.stack.push(x);
};
/**
* @returns {void}
*/
Stack.prototype.pop = function() {
this.stack.pop();
};
/**
* @returns {number}
*/
Stack.prototype.top = function() {
return this.stack[this.stack.length - 1];
};
/**
* @returns {boolean}
*/
Stack.prototype.empty = function() {
return !this.stack.length;
};