Output of joining 2 arrays does not come as expected

Question

Given two arrays, arr1 and arr2, that have been sorted in descending order, output an array which appends the values from both arr1 and arr2 while being sorted in descending order.

MyApproach

I found 2 -3 links helpful and I noticed that I have a similar kind of code here.But I am unable to get the expected output.

One of my Resources:How to merge two sorted arrays into a sorted array?

Can Anyone guide me what I am doing wrong.

I have made the code for length of array1 >= length of array2 for other part I will append later

public int[] join(int[] arr1,int[] arr2)
{
   int l1=arr1.length;
   int l2=arr2.length;
   int i=0,j=0,k=0;
   int c[]=new int[arr1.length+arr2.length];
   if(l1>=l2)
   {
    for(;i<arr1.length;)
    {
        if(arr1[i]>=arr2[j])
        {
            c[k]=arr1[i++];
            System.out.println(c[k]);
            k++;

        }
        else if(arr2[j]>arr1[i])
        {
            c[k]=arr2[j++];
            System.out.println(c[k]);
            k++;
        }

    } 

    //System.out.println(j);
    //System.out.println(i);


        while(i<arr1.length)
        {
         c[k]=arr1[i++];
         System.out.println(c[k]);

         k++;
        }
        while(j<arr2.length)
        {

         c[k]=arr2[j++];
         System.out.println(c[k]);

         k++;
        }`
    } 


     return c;

  //write your code here

}

  Parameters                     ActualOut                     Expected Out

{100,90,80,70,60}null {105,100,95,90,85,80,75,70,65,60} {105,95,85,75,65}

Answer 1

While I think Elliot's answer is the best way to go, I have some suggestions for how to stick with your code and make it work.

First, in your for loop towards the start of your function, have the condition be i < l1 && j < l2, instead of only checking i (also, if you're going to declare variables for the arrays' lengths, use them!). This allows you to get rid of the if (l1 >= l2) check that you have, making it work regardless of which array is longer.

Otherwise, your code seems fully functional. One additional tip that I would suggest would be to make your join method static. This allows you to call it independently, by simply calling join (someArr1, someArr2) instead of SomeObject.join(someArr1, someArr2) (since all of the variables used in join are local, not instance variables of SomeObject.

Answer 2

This may be the best argument in favor of the conditional operator ? : (a ternary operation). To your question, you need to guard against null input. Then you could take advantage of System.arraycopy(Object src, int srcPos, Object dest, int destPos, int length) to copy the remaining elements after you loop. Something like

public static int[] join(int[] arr1, int[] arr2) {
    if (arr1 == null) {
        return arr2;
    } else if (arr2 == null) {
        return arr1;
    }
    int p = 0, i = 0, j = 0;
    int[] out = new int[arr1.length + arr2.length];
    while (i < arr1.length && j < arr2.length) {
        out[p++] = (arr1[i] > arr2[j]) ? arr1[i++] : arr2[j++];
    }
    if (i < arr1.length) {
        System.arraycopy(arr1, i, out, p, arr1.length - i);
    } else if (j < arr2.length) {
        System.arraycopy(arr2, j, out, p, arr2.length - j);
    }
    return out;
}

Which I tested like

public static void main(String args[]) {
    int[][] tests = { { 3, 2, 1 }, { 10, 9, 7 }, { 6, 5, 4 } };
    System.out.println(Arrays.toString(join(tests[0], join(tests[1], tests[2]))));
}

And, I got

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