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LeetCode-225-Implement-Stack-using-Queues.java
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LeetCode-225-Implement-Stack-using-Queues.java
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class MyStack
{
Queue<Integer> queue;
public MyStack()
{
this.queue=new LinkedList<Integer>();
}
// Push element x onto stack.
public void push(int x)
{
queue.add(x);
for(int i=0;i<queue.size()-1;i++)
{
queue.add(queue.poll());
}
}
// Removes the element on top of the stack.
public int pop()
{
return queue.poll();
}
// Get the top element.
public int top()
{
return queue.peek();
}
// Return whether the stack is empty.
public boolean empty()
{
return queue.isEmpty();
}
}
// 2. Deque (not allowed to use deque, as removeFirst() is not standard Queue operation)
// class MyStack {
// Deque<Integer> dq;
// /** Initialize your data structure here. */
// public MyStack() {
// dq = new ArrayDeque<>();
// }
// /** Push element x onto stack. */
// public void push(int x) {
// dq.offerFirst(x);
// }
// /** Removes the element on top of the stack and returns that element. */
// public int pop() {
// return dq.removeFirst();
// }
// /** Get the top element. */
// public int top() {
// return dq.peekFirst();
// }
// /** Returns whether the stack is empty. */
// public boolean empty() {
// return dq.isEmpty();
// }
// }
/**
* Your MyStack object will be instantiated and called as such:
* MyStack obj = new MyStack();
* obj.push(x);
* int param_2 = obj.pop();
* int param_3 = obj.top();
* boolean param_4 = obj.empty();
*/