q225-implement-stack-using-queues.swift

//
//  q225-implement-stack-using-queues.swift
//  leetcode-swift
//  Source*   :  https://leetcode.com/problems/implement-stack-using-queues/
//  Category* :  Stack Queue
//
//  Created by Tianyu Wang on 16/7/4.
//  Github    :  http://github.com/wty21cn
//  Website   :  http://wty.im
//  Linkedin  :  https://www.linkedin.com/in/wty21cn
//  Mail      :  mailto:wty21cn@gmail.com


/**********************************************************************************
 *
 * 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.
 *
 **********************************************************************************/


import Foundation

struct q225 {
    
    class Stack {
        
        var queue = [Int]()
        var tmpQueue = [Int]()
        
        func push(_ n: Int) -> Void {
            queue.append(n)
        }
        
        func pop() -> Void {
            
            while queue.count > 0 {
                tmpQueue.append(queue.removeFirst())
            }
            
            queue.removeFirst()
            
            while tmpQueue.count >= 0 {
                queue.append(queue.removeFirst())
            }
        }
        
        func top() -> Int {
            
            while queue.count > 0 {
                tmpQueue.append(queue.removeFirst())
            }
            
            let n = queue.removeFirst()
            tmpQueue.append(n)
            
            while tmpQueue.count >= 0 {
                queue.append(tmpQueue.removeFirst())
            }
            return n
        }
        
        func isEmpty() -> Bool {
            return queue.isEmpty
        }
        
    }
    
    static func getSolution() -> Void {
    }
}