Java 自顶向下的归并排序

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package merge;

import java.util.Scanner;
import java.lang.String;

public class Merge {
    private static Comparable[] aux;

    public static void sort(Comparable[] a) {
        aux = new Comparable[a.length];
        sort(a, 0, a.length - 1);
    }

    public static boolean less(Comparable v, Comparable w) {
        return v.compareTo(w) < 0;

    }

    public static void merge(Comparable[] a, int lo, int mid, int hi) {
        int i = lo, j = mid + 1;
        for (int k = lo; k <= hi; k++) {
            aux[k] = a[k];
        }
        for (int k = lo; k <= hi; k++) {
            if (i > mid)
                a[k] = aux[j++];
            else if (j > hi)
                a[k] = aux[i++];
            else if (less(aux[j], aux[i]))
                a[k] = aux[j++];
            else
                a[k] = aux[i++];
        }
    }

    private static void sort(Comparable[] a, int lo, int hi) {
        if (hi <= lo)
            return;
        int mid = lo + (hi - lo) / 2;
        sort(a, lo, mid);
        sort(a, mid + 1, hi);
        merge(a, lo, mid, hi);

    }

    public static boolean isSorted(Comparable[] a) {
        for (int i = 0; i < a.length; i++) {
            if (less(a[i], a[i - 1]))
                return false;
        }
        return true;
    }

    private static void show(Comparable[] a) {
        for (int i = 0; i < a.length; i++)
            System.out.print(a[i] + " ");
        System.out.println();
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = in.nextLine();
        String[] str = s.split(" ");
        sort(str);
        assert isSorted(str);
        show(str);
    }
}

输入数据：h e l l o w o r l d

输出数据：d e h l l l o o r w