LeetCode : 232. Implement Queue using Stacks

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https://leetcode.com/problems/implement-queue-using-stacks/

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class MyQueue {

    Stack<Integer> p;
    Stack<Integer> q;
    /** Initialize your data structure here. */
    public MyQueue() {
        p = new Stack();
        q = new Stack();
    }

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

    /** Removes the element from in front of queue and returns that element. */
    public int pop() {
        if (q.isEmpty())
            while(!p.isEmpty()) q.push(p.pop());

        return q.pop();
    }

    /** Get the front element. */
    public int peek() {
        if (q.isEmpty())
            while(!p.isEmpty()) q.push(p.pop());

        return q.peek();
    }

    /** Returns whether the queue is empty. */
    public boolean empty() {
        return p.isEmpty() && q.isEmpty();// !!!
    }
}

/**
 * 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();
 */

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