package sorting;
/**
 * 归并排序
 * 平均O(nlogn),最好O(nlogn),最坏O(nlogn);空间复杂度O(n);稳定;较复杂
 * @author zeng
 *
 */
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);
 }
}