1 import java.util.ArrayDeque;
2 import java.util.Queue;
3
4 public class StackByQueue {
5 private Queue<Integer> inQueue;
6 private Queue<Integer> outQueue;
7 private Queue<Integer> tempQueue = null;
8
9 /**
10 * Initialize your data structure here.
11 */
12 public StackByQueue() {
13 this.inQueue = new ArrayDeque<>();
14 this.outQueue = new ArrayDeque<>();
15 }
16
17
18 /**
19 * Push element x onto stack.
20 */
21 public void push(int x) {
22 inQueue.offer(x);
23 while (!outQueue.isEmpty()) {
24 inQueue.offer(outQueue.poll());
25 }
26 tempQueue = inQueue;
27 inQueue = outQueue;
28 outQueue = tempQueue;
29
30 }
31
32 /**
33 * Removes the element on top of the stack and returns that element.
34 */
35 public int pop() {
36 return outQueue.poll();
37 }
38
39 /**
40 * Get the top element.
41 */
42 public int top() {
43 return outQueue.peek();
44 }
45
46 /**
47 * Returns whether the stack is empty.
48 */
49 public boolean empty() {
50 return outQueue.isEmpty();
51 }
52
53
54 public static void main(String[] args) {
55 StackByQueue obj = new StackByQueue();
56 obj.push(1);
57 obj.push(2);
58
59 int param_2 = obj.pop();
60 int param_3 = obj.top();
61 boolean param_4 = obj.empty();
62 }
63
64 }
