Merge

简书 賈小強
转载请注明原创出处，谢谢！

package com.lab1.test2;

public class Merge {
    public static void main(String[] args) {
        Comparable[] a = { 5, 3, 1, 2, 4 };
        sort(a);
        show(a);
    }

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

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

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

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

    private static void exch(Comparable[] a, int i, int j) {
        Comparable temp = a[i];
        a[i] = a[j];
        a[j] = temp;
    }

    private static boolean less(Comparable[] a, int i, int j) {
        return a[i].compareTo(a[j]) < 0;
    }
}

输出

1 2 3 4 5 

Happy learning !!