对整型数组排序（水题、锻炼一下归并排序的写法）

import java.util.Scanner;

/*
    输入整型数组和排序标识，对其元素按照升序或降序进行排序
    int  iSortFlag：排序标识：0表示按升序，1表示按降序
 */
public class Homework_1 {
    static int flag;

    public static void mergeSort(int[] arr) {
        if (arr == null || arr.length < 2) {
            return;
        }
        process(arr, 0, arr.length - 1);
    }

    public static void process(int[] arr, int L, int R) {
        if (L == R) {
            return;
        }
        int mid = L + ((R - L) >> 1);
        process(arr, L, mid);
        process(arr, mid + 1, R);
        merge(arr, L, mid, R);
    }

    public static void merge(int[] arr, int L, int mid, int R) {
        int[] help = new int[R - L + 1];         //辅助数组
        int i = 0;
        int p1 = L;
        int p2 = mid + 1;
        while (p1 <= mid && p2 <= R) {
            if (flag == 0) {
                help[i++] = arr[p1] <= arr[p2] ? arr[p1++] : arr[p2++];
            }
            if (flag == 1) {
                help[i++] = arr[p1] > arr[p2] ? arr[p1++] : arr[p2++];
            }
        }
        while (p1 <= mid) {
            help[i++] = arr[p1++];
        }
        while (p2 <= R) {
            help[i++] = arr[p2++];
        }
        for (i = 0; i < help.length; i++) {
            arr[L + i] = help[i];
        }
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int[] arr;
        while (sc.hasNext()) {
            int n = sc.nextInt();
            arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = sc.nextInt();
            }
            flag = sc.nextInt();
            if (flag == 0) {
                mergeSort(arr);
            }
            if (flag == 1) {
                mergeSort(arr);
            }
            for (int i = 0; i < arr.length; i++) {
                if (i < arr.length - 1) {
                    System.out.print(arr[i] + " ");
                } else {
                    System.out.println(arr[i]);
                }
            }
        }
    }
}