MergeSort.java

import java.util.Arrays;

/**
 * Created by Connor on 3/1/16.
 */
public class MergeSort {
    static int lc,rc;//static counters

    public static int[] mergeSort(int[] arr){
        if (arr.length <= 1) return arr;       //base case
        else {
            int middleRight = (int)Math.ceil(arr.length/2.0);
            int[] left,right;                  //cutting array in half (if array is an odd # -> left half gets extra #)

            left = Arrays.copyOf(arr,middleRight);
            right = Arrays.copyOfRange(arr,middleRight,arr.length);

            left = mergeSort(left);            //the recursive call returns the left half of original data sorted
            right = mergeSort(right);          //the recursive call returns the right half of original data sorted

            return merge(left,right);          //merges the two sorted halves
        }
    }

    private static int[] merge(int[] leftSide, int[] rightSide){
        int[] result = new int[leftSide.length + rightSide.length];
        lc = 0; rc = 0;  //sets the counters of each array (static ints) to 0

        for (int i = 0; i < result.length; i++) {

            if (lc != leftSide.length && (rc == rightSide.length || rightSide[rc] > leftSide[lc])){
                result[i] = leftSide[lc++];
            }
            else result[i] = rightSide[rc++];
        }
        return result;
    }

    public static void printArray(int[] a){
        for (int n:a) {
            System.out.print("[" + n + "] ");
        }
        System.out.println();
    }
    
    public static int[] arrayGenerator(int size, int min, int max){
        int[] result = new int[size];
        for (int i = 0; i < size; i++) {
            result[i] =  min + (int)(Math.random() * ((max - min) + 1));
        }
        return result;
    }

}