归并排序算法

    public static int[] mergeSort(int a[], int low, int high) {
        int mid = (low + high) / 2;
        if (low < high) {
            mergeSort(a, low, mid);
            mergeSort(a, mid + 1, high);
            merge(a, low, mid, high);
        }
        return a;
    }

    public static void merge(int a[], int low, int mid, int high) {
        int[] tem = new int[high - low + 1];
        int k = 0;
        int i = low, j = mid + 1;
        while (i <= mid && j <= high) {
            if (a[i] < a[j]) {
                tem[k++] = a[i++];
            } else {
                tem[k++] = a[j++];
            }
        }
        while (i <= mid) {
            tem[k++] = a[i++];
        }
        while (j <= high) {
            tem[k++] = a[j++];
        }
        for (int l = 0; l < tem.length; l++) {
            a[low + l] = tem[l];
        }
    }