com.ericgithinji.java.algorithms.sort.MergeSort.java Source code

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Here is the source code for com.ericgithinji.java.algorithms.sort.MergeSort.java

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package com.ericgithinji.java.algorithms.sort;

import org.apache.commons.lang3.ArrayUtils;

/**
 *
 * @author eric
 */
public class MergeSort {

    private MergeSort() {
    };

    public static int[] mergeSort(int[] array) {
        if (array.length == 1)
            return array;
        int newLength = array.length / 2;
        int[] leftArray = new int[newLength];
        int[] rightArray = new int[newLength];
        System.arraycopy(array, 0, leftArray, 0, newLength);
        System.arraycopy(array, newLength, rightArray, 0, newLength);
        leftArray = mergeSort(leftArray);
        rightArray = mergeSort(rightArray);

        return merge(leftArray, rightArray);
    }

    //    Merge
    public static int[] merge(int[] array1, int array2[]) {
        int[] mergedArray = new int[array1.length + array2.length];
        int i = mergedArray.length - 1;
        if (mergedArray.length <= 1)
            return mergedArray;
        if (mergedArray.length > 1) {
            if (array1[0] > array2[0]) {
                mergedArray[i] = array2[0];
                mergedArray = ArrayUtils.removeElement(array2, array2[0]);
                i--;
            } else {
                mergedArray[i] = array1[0];
                mergedArray = ArrayUtils.removeElement(array1, array1[0]);
                i--;
            }
        }
        if (array1.length > 0) {
            mergedArray[i] = array1[0];
            mergedArray = ArrayUtils.removeElement(array1, array1[0]);
            i--;
        }
        if (array2.length > 0) {
            mergedArray[i] = array2[0];
            mergedArray = ArrayUtils.removeElement(array2, array2[0]);
            i--;
        }
        return mergedArray;
    }
}