1 package POJ;
2
3 public class Main {
4
5 /**
6 *
7 * MergeSort
8 *
9 */
10 public static void main(String[] args) {
11 Main so = new Main();
12 int[] list = { 6, 4, 2, 3, 1, 5, 10, 4, 9, 8, 11, 7 };
13 int[] result = so.mergeSort(list);
14 for (int a : result)
15 System.out.println(a);
16 }
17
18 public int[] mergeSort(int[] list) {
19 int[] helper = new int[list.length];
20 mergeSort(list, helper, 0, list.length - 1);
21 return list;
22 }
23
24 private void mergeSort(int[] list, int[] helper, int low, int high) {
25 // TODO Auto-generated method stub
26 if (low < high) {
27 int mid = (high + low) / 2;
28 mergeSort(list, helper, low, mid);
29 mergeSort(list, helper, mid + 1, high);
30 merge(list, helper, low, mid, high);
31 }
32 }
33
34 private void merge(int[] list, int[] helper, int low, int mid, int high) {
35 // TODO Auto-generated method stub
36 for (int i = low; i <= high; i++) {
37 helper[i] = list[i];
38 }
39 int helperLeft = low;
40 int helperRight = mid + 1;
41 int current = low;
42 while (helperLeft <= mid && helperRight <= high) {
43 if (helper[helperLeft] <= helper[helperRight]) {
44 list[current] = helper[helperLeft];
45 helperLeft++;
46 } else {
47 list[current] = helper[helperRight];
48 helperRight++;
49 }
50 current++;
51 }
52 int remaining = mid - helperLeft;
53 for (int i = 0; i <= remaining; i++) {
54 list[current + i] = helper[helperLeft + i];
55 }
56 }
57 }
