Merge Sort

MergeSort

package com.sorting.merge;

import static com.sorting.insert.SortUtils.less;

public class MergeSort {

  public Comparable[] sort(Comparable[] items) {
		
		sort (items,new Comparable[items.length], 0, items.length-1);
		
		return items;
	}
	
	public void sort (Comparable[] input, Comparable[] aux, int lowIndex, int highIndex){
		if (highIndex<=lowIndex) return;
		int midIndex=lowIndex+(highIndex-lowIndex)/2;
		sort (input, aux, lowIndex,   midIndex);
		sort (input, aux, midIndex+1, highIndex);
		
		merge (input, aux, lowIndex, midIndex, highIndex);
		
		
	}
	
	public void merge(Comparable[] input, Comparable[] aux, int lowIndex, int midIndex, int highIndex){
		
		if (input==null || aux==null){
			throw new IllegalArgumentException("Input or Auxillary array are null");
		}
		
		for (int temp=lowIndex;temp<=highIndex;temp++){
			aux[temp]=input[temp];
		}
		
		int i=lowIndex,j=midIndex+1;
		
		for (int counter=lowIndex;counter<=highIndex;counter++){
			if (i>midIndex){
				input[counter]=aux[j];
				j++;
			}
			else if (j>highIndex){
				input[counter]=aux[i];
				i++;
			}
			else if (less(aux[j], aux[i])){
				input[counter]=aux[j];
				j++;
			}
			else{
				input[counter]=aux[i];
				i++;
			}
		}
		
		
		
	}

}