-
Notifications
You must be signed in to change notification settings - Fork 0
/
225. Stack using Queues
65 lines (56 loc) · 1.43 KB
/
225. Stack using Queues
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
/*
https://leetcode.com/problems/implement-stack-using-queues/description/
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.
*/
class MyStack {
private Queue<Integer> queue;
int size = 0;
/**
* Initialize your data structure here.
*/
public MyStack() {
queue = new ArrayDeque<>();
}
/**
* Push element x onto stack.
*/
public void push(int x) {
queue.add(x);
size++;
}
/**
* Removes the element on top of the stack and returns that element.
*/
public int pop() {
for (int i = 0; i < size - 1; i++) {
int temp = queue.poll();
queue.add(temp);
}
size--;
return queue.poll();
}
/**
* Get the top element.
*/
public int top() {
for (int i = 0; i < size - 1; i++) {
int temp = queue.poll();
queue.add(temp);
}
int top = queue.poll();
queue.add(top);
return top;
}
/**
* Returns whether the stack is empty.
*/
public boolean empty() {
return queue.isEmpty();
}
}