归并排序（java）

public class MergeSort {
    public static void mergeSort(int[] array, int from, int to) {
        if (from < to) {
            int middle = (int) Math.floor((to + from) / 2);
            mergeSort(array, from, middle);
            mergeSort(array, middle + 1, to);
            merge(array, from, middle, to);
        }
    }
    private static void merge(int[] array, int from, int middle, int to) {
        int[] leftArray = new int[middle - from + 1];
        int[] rightArray = new int[to - middle];
        for (int i = 0; i < leftArray.length; i++) {
            leftArray[i] = array[from + i];
        }
        for (int i = 0; i < rightArray.length; i++) {
            rightArray[i] = array[middle + i + 1];
        }
        int idxL = 0;
        int idxR = 0;
        for (int idx = from; idx <= to; idx++) {
            if (leftArray[idxL] <= rightArray[idxR]) {
                array[idx] = leftArray[idxL];
                idxL++;
                if (idxL == leftArray.length) {
                    copyRest(array, idx + 1, rightArray, idxR);
                    return;
                }
            } else {
                array[idx] = rightArray[idxR];
                idxR++;
                if (idxR == rightArray.length) {
                    copyRest(array, idx + 1, leftArray, idxL);
                    return;
                }
            }
        }
    }
    /**
     * 把oriArr数组中的内容从oIdex开始复制到desArr中，从dIdx开始复制
     */
    private static void copyRest(int[] desArr, int dIdx, int[] oriArr, int oIdx) {
        for (; oIdx < oriArr.length; oIdx++) {
            desArr[dIdx] = oriArr[oIdx];
            dIdx++;
        }
    }
    public static void main(String[] args) {
        int[] a = { 44, 32, 15, 69, 1, 34, 25, 62, 3, 66, 8, 12, 22, 7, 9, -8 };
        MergeSort.mergeSort(a, 0, a.length - 1);
        for (int i = 0; i < a.length; i++) {
            System.out.print(a[i] + " ");
        }
    }
}