225. Implement Stack using Queues

class MyStack {
// Push element x onto stack.
Queue<Integer> q1 = new LinkedList<Integer>();
Queue<Integer> q2 = new LinkedList<Integer>();
public void push(int x) {
q1.add(x);
while(!q2.isEmpty()){
q1.add(q2.poll());
}
while(!q1.isEmpty()){
q2.add(q1.poll());
}
}
// Removes the element on top of the stack.
public void pop() {
q2.poll();
}
// Get the top element.
public int top() {
return q2.peek();
}
// Return whether the stack is empty.
public boolean empty() {
return q1.isEmpty() && q2.isEmpty();
}
}
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