mergeSort

 package POJ;

 public class Main {

     /**
      *
      * MergeSort
      *
      */
     public static void main(String[] args) {
         Main so = new Main();
         int[] list = { 6, 4, 2, 3, 1, 5, 10, 4, 9, 8, 11, 7 };
         int[] result = so.mergeSort(list);
         for (int a : result)
             System.out.println(a);
     }

     public int[] mergeSort(int[] list) {
         int[] helper = new int[list.length];
         mergeSort(list, helper, 0, list.length - 1);
         return list;
     }

     private void mergeSort(int[] list, int[] helper, int low, int high) {
         // TODO Auto-generated method stub
         if (low < high) {
             int mid = (high + low) / 2;
             mergeSort(list, helper, low, mid);
             mergeSort(list, helper, mid + 1, high);
             merge(list, helper, low, mid, high);
         }
     }

     private void merge(int[] list, int[] helper, int low, int mid, int high) {
         // TODO Auto-generated method stub
         for (int i = low; i <= high; i++) {
             helper[i] = list[i];
         }
         int helperLeft = low;
         int helperRight = mid + 1;
         int current = low;
         while (helperLeft <= mid && helperRight <= high) {
             if (helper[helperLeft] <= helper[helperRight]) {
                 list[current] = helper[helperLeft];
                 helperLeft++;
             } else {
                 list[current] = helper[helperRight];
                 helperRight++;
             }
             current++;
         }
         int remaining = mid - helperLeft;
         for (int i = 0; i <= remaining; i++) {
             list[current + i] = helper[helperLeft + i];
         }
     }
 }