Question

I have my own ArrayQueue Class which has methods for enqueue, dequeue and peek etc. My ArrayQmerge class extends this Class and contains:

    public void mergeQs(ArrayQmerge q){

    }

I was wondering whats the best way to write a method to merge an ArrayQueue with another Queue without removing any elements from the q thats passed.

eg. queue1 = [1,2,3,4,11] and queue2 = [5,6,7,8,9,10,12].
When queue1.mergeQs(queue2) is called it will create queue1 = [1,5,2,6,3,7,4,8,11,9,10,12] whilst queue2 would remain [5,6,7,8,9,10,12]

I want the mergeQs method to interleave the elements from the two queues if that makes sense. I know how to successfully add them together or using a method which passes both Queues as arguments but in this case i want to use the above method(which only passes one)…

Answer 1

This is what you can do:

public static void main(String[] args) {
    ArrayQmerge q1 = new ArrayQmerge();
    q1.enqueue(1);
    q1.enqueue(2);
    q1.enqueue(3);
    q1.enqueue(4);
    q1.enqueue(11);
    ArrayQmerge q2 = new ArrayQmerge();
    q2.enqueue(5);
    q2.enqueue(6);
    q2.enqueue(7);
    q2.enqueue(8);
    q2.enqueue(9);
    q2.enqueue(10);
    q2.enqueue(12);
    System.out.println(q1);
    System.out.println(q2);
    q1.mergeQs(q2);
    System.out.println(q1);
    System.out.println(q2);
}

static class ArrayQmerge{
    private List<Integer> queue = new ArrayList<Integer>();

    public void enqueue(int val){
        queue.add(val);
    }

    public String toString(){
        return queue.toString();
    }

    public void mergeQs(ArrayQmerge q){
        List<Integer> mergedQ = new ArrayList<Integer>(this.queue.size() + q.queue.size());
        for (int i = 0, j = 0; i < this.queue.size() || j < q.queue.size();){
            if (i < this.queue.size())
                mergedQ.add(this.queue.get(i++));
            if (j < q.queue.size())
                mergedQ.add(q.queue.get(j++));
        }
        this.queue = mergedQ;
   }
}

Here is output:

[1, 2, 3, 4, 11]
[5, 6, 7, 8, 9, 10, 12]
[1, 5, 2, 6, 3, 7, 4, 8, 11, 9, 10, 12]
[5, 6, 7, 8, 9, 10, 12]