学步园

原理：

代码和上图没关系：

package com.lyj.sort;

public class MergeSort {

    /**
     * @param args
     */
    public static void main(String[] args) {
        int[] array = { 1, 8, 6, 4, 10, 5, 3, 2, 22 };

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

    private static void mergeSort(int[] array, int start, int end) {
        if (start < end) {
            int mid = (start + end) / 2;

            mergeSort(array, start, mid);
            mergeSort(array, mid + 1, end);
            merge(array, start, mid, end);

            // 打印每次排序
            for (int i : array) {
                System.out.print(i + " ");
            }
            System.out.println();
        }
    }

    private static void merge(int[] array, int start, int mid, int end) {
        int[] temp = new int[end - start + 1];
        int i = 0;
        int j = start;
        int k = mid + 1;

        // array的左子树和右子树都有元素
        while (j <= mid && k <= end) {
            if (array[j] >= array[k]) {
                temp[i++] = array[k++];
            } else {
                temp[i++] = array[j++];
            }
        }

        // 将array的剩余元素装入temp
        while (j <= mid)
            temp[i++] = array[j++];
        while (k <= end)
            temp[i++] = array[k++];

        // 将temp的元素装入array
        for (int h = 0; h < temp.length; h++) {
            array[start + h] = temp[h];
        }
    }

}

排序过程：