归并排序（稳定排序）

 1 public class MergeSort {
 2     public static void main(String[] args) {
 3         int[] arr = {9,6,11,3,5,12,8,7,10,15,14,4,1,13,2};
 4         int[] temp = new int[arr.length];
 5         sort(arr,0,arr.length-1,temp);
 6         print(arr);
 7     }
 8     static void sort(int[]arr,int left, int right,int[] temp) {
 9         int mid = (right-left)/2+left;
10         if(left<right) {
11             sort(arr,left,mid,temp);//分，自顶向下，递归
12             sort(arr,mid+1,right,temp);
13         }
14         merge(arr,temp,left,right);//治，和，回溯
15     }
16     static void merge(int[] arr,int[] temp,int left,int right) {
17         int k =0;
18         int mid = (right-left)/2+left;
19         int Left = left;//左序列指针
20         int Mid = mid+1;//右序列指针
21         
22         while(Mid<=right && Left<= mid) temp[k++] = arr[Left]<=arr[Mid] ? arr[Left++] : arr[Mid++];
23         while(Mid<=right) temp[k++] = arr[Mid++];//两正序数组合并一正序数组
24         while(Left<=mid) temp[k++] = arr[Left++];
25         
26         Left = left;//初始化，将合并后的正序数组给原数组传回排好序的值
27         for(int i = 0; i<right-left+1;i++) {
28             arr[Left++] = temp[i];
29         }
30     }
31     static void swap(int[] arr,int i,int j) {
32         int temp=arr[i];
33         arr[i]=arr[j];
34         arr[j]=temp;
35     }
36     static void print(int[] arr) {
37         for(int i=0;i<arr.length;i++) {
38             System.out.print(arr[i]+" ");
39         }
40     }
41 }