Java排序算法之归并排序简单实现

算法描述：对于给定的一组记录，首先将每两个相邻的长度为1的子序列进行归并，得到 n/2（向上取整）个长度为2或1的有序子序列，再将其两两归并，反复执行此过程，直到得到一个有序序列。

package sorting;public class MergeSort {public static void merge(int[] a, int start, int mid,      int end) {int[] tmp = new int[a.length];System.out.println("merge " + start + "~" + end);int i = start, j = mid + 1, k = start;while (i != mid + 1 && j != end + 1) {if (a[i] < a[j])        tmp[k++] = a[i++]; else        tmp[k++] = a[j++];}while (i != mid + 1)      tmp[k++] = a[i++];while (j != end + 1)      tmp[k++] = a[j++];for (i = start; i <= end; i++)      a[i] = tmp[i];for (int p : a)      System.out.print(p + " ");System.out.println();}static void mergeSort(int[] a, int start, int end) {if (start < end) {int mid = (start + end) / 2;mergeSort(a, start, mid);// 左边有序mergeSort(a, mid + 1, end);// 右边有序merge(a, start, mid, end);}}public static void main(String[] args) {int[] b = { 49, 38, 65, 97, 76, 13, 27, 50 };mergeSort(b, 0, b.length - 1);}}