Java数据结构与算法：归并排序

package com.mindle.test.sort;

import java.util.Arrays;

public class MergeSort<AnyType extends Comparable<? super AnyType>> {

    public void mergeSort(AnyType[] array) {
        AnyType[] tmpArray = (AnyType[]) new Comparable[array.length]; // 缓存数组

        mergeSort(array, tmpArray, 0, array.length - 1);
    }

    /**
     * 递归调用的归并排序，分而治之：分成左右两半，分别排序后，再合并
     * 
     * @param array
     *            目标数组
     * @param tmpArray
     *            缓存数组
     * @param left
     *            数组头
     * @param right
     *            数组尾
     */
    private void mergeSort(AnyType[] array, AnyType[] tmpArray, int left, int right) {

        // 一个元素时不用排序
        if (left < right) {
            int mid = (left + right) / 2;
            mergeSort(array, tmpArray, left, mid);
            mergeSort(array, tmpArray, mid + 1, right);
            merge(array, tmpArray, left, mid + 1, right);
        }

    }

    /**
     * 将两个排好序的数组合并成一个有序数组
     * 
     * @param array
     *            目标数组
     * @param tmpArray
     *            缓存数组
     * @param leftPos
     *            第一个数组头
     * @param rightPos
     *            第二个数组头
     * @param rightEnd
     *            第二个数组尾
     */
    private void merge(AnyType[] array, AnyType[] tmpArray, int leftPos, int rightPos, int rightEnd) {
        int leftEnd = rightPos - 1;
        int tmpPos = leftPos;
        int num = rightEnd - leftPos + 1;

        while (leftPos <= leftEnd && rightPos <= rightEnd) {
            if (array[leftPos].compareTo(array[rightPos]) < 0)
                tmpArray[tmpPos++] = array[leftPos++];
            else
                tmpArray[tmpPos++] = array[rightPos++];
        }

        while (rightPos <= rightEnd) {
            tmpArray[tmpPos++] = array[rightPos++];
        }

        while (leftPos <= leftEnd) {
            tmpArray[tmpPos++] = array[leftPos++];
        }

        // 复制回数组
        for (int i = 0; i < num; i++, rightEnd--)
            array[rightEnd] = tmpArray[rightEnd];
    }

    // test
    public static void main(String[] args) {
        Integer[] array = { 34, 8, 64, 51, 32, 21, 25, 58, 78, 1, 5, 12, 2, 34, 8, 64, 51, 32, 21, 25, 58, 78, 1, 5, 12,
                2, 34, 8, 64, 51, 32, 21, 25, 58, 78, 1, 5, 12, 2 };
        System.out.println(Arrays.toString(array));
        new MergeSort<Integer>().mergeSort(array);
        System.out.println(Arrays.toString(array));
    }

}