class MyQueue {
/** Initialize your data structure here. */
private Stack<Integer> s1 = null;
private Stack<Integer> s2 = null;
public MyQueue() {
s1 = new Stack();
s2 = new Stack();
}
/** Push element x to the back of queue. */
public void push(int x) {
s1.push(x);
}
/** Removes the element from in front of queue and returns that element. */
public int pop() {
if(s2.isEmpty()) {
while(!s1.isEmpty()) {
s2.push(s1.pop());
}
}
return s2.pop();
}
/** Get the front element. */
public int peek() {
if(s2.isEmpty()) {
while(!s1.isEmpty()) {
s2.push(s1.pop());
}
}
return s2.peek();
}
/** Returns whether the queue is empty. */
public boolean empty() {
return s1.isEmpty() && s2.isEmpty();
}
}