LeetCode-232 Implement Queue using Stacks Solution (with Java)

1. Description:

Notes: 

2. Examples:

3.Solutions:

/**
 * Created by sheepcore on 2019-03-07
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue obj = new MyQueue();
 * obj.push(x);
 * int param_2 = obj.pop();
 * int param_3 = obj.peek();
 * boolean param_4 = obj.empty();
 */
class MyQueue {
    /** Initialize your data structure here. */
    Stack<Integer> input = new Stack<Integer>();
    Stack<Integer> output = new Stack<Integer>();

    /** Push element x to the back of queue. */
    public void push(int x) {
        input.push(x);
    }

    /** Removes the element from in front of queue and returns that element. */
    public int pop() {
        peek();
        return output.pop();
    }

    /** Get the front element. */
    public int peek() {
       if(output.empty()){
           while (!input.empty()){
               output.push(input.pop());
           }
       }
       return output.peek();
    }

    /** Returns whether the queue is empty. */
    public boolean empty() {
        return input.empty() && output.empty();
    }
}