Mergesort in java

Question

I am new to Java and have tried to implement mergesort in Java. However, even after running the program several times, instead of the desired sorted output, I am getting the

Answer 1

The problem lies here:

A = merge(leftArray,rightArray);

Now your merge array does this:

static int[] merge(int[] l, int[] r) {
    int[] a = new int[totElem];
    // bunch of code
    return a;
}

When you started, A was a reference to inputArray. But then you reassigned it to be whatever came out of merge. Unfortunately, that doesn't touch what inputArray is in the main method. That basically says "Oh look at all the work you did... throw it away!"

You could change that with something like

static int[] mergeSort(int[] A) {
    // A = merge... // not this
    return merge... // use this
}

Then in your main method, you can do

int[] merged = mergeSort(inputArray);
for(int i : merged) System.out.println(i);