1 package sort;
2 //归并排序
3 public class MergeSortTest {
4 public static void main(String[] args){
5 int[] data = new int[]{5, 3, 6, 2, 1, 9, 4, 8, 7};
6 mergeSort(data);
7 System.out.println("排序后的数组：");
8 print(data);
9 }
10
11 public static void mergeSort(int[] data){
12 sort(data, 0, data.length-1);
13 }
14
15 public static void sort(int[] data, int left, int right){
16 if (left >= right)
17 return;
18 int center = (left + right) / 2;
19 sort(data, left, center);
20 sort(data, center+1, right);
21 merge(data, left, center, right);
22 print(data);
23 }
24
25 public static void merge(int[] data, int left, int center, int right){
26 //临时数组
27 int[] tempArr = new int[data.length];
28 //右边数组的第一个元素索引
29 int mid = center + 1;
30 //tempIndex记录临时数组的索引
31 int tempIndex = left;
32 //缓存左数组的第一个元素的索引
33 int tmp = left;
34
35 while(left <= center && mid <=right){
36 if (data[left] <= data[mid]){
37 tempArr[tempIndex++] = data[left++];
38 }else{
39 tempArr[tempIndex++] = data[mid++];
40 }
41 }
42
43 //剩余部分依次放入临时数组(实际上两个while只会执行其中一个)
44 while (mid <= right){
45 tempArr[tempIndex++] = data[mid++];
46 }
47
48 while (left <= center){
49 tempArr[tempIndex++] = data[left++];
50 }
51
52 //将临时数组中的内容拷贝回原数组中
53 while (tmp <= right){
54 data[tmp] = tempArr[tmp++];
55 }
56 }
57
58 public static void print(int[] data){
59 for(int i=0; i<data.length; i++){
60 System.out.print(data[i]+" ");
61 }
62 System.out.println();
63 }
64 }
