/*
*遞迴 歸併排序
*/
#include<iostream>
using namespace std;
void Merge(int *, int , int, int *);

void Merge_Sort(int *data, const int start, const int end, int * result )
{
  if( 1 == end - start)//只有兩個元素
  {
	  if(data[start] > data[end])
	  {
	    int temp = data[start];
		data[start] = data[end];
		data[end] = temp;
	  }
	  return;
  }
 
  else if(0 == end - start){
      return;
   }
  else
  {
    Merge_Sort(data, start, (end - start +1)/2 + start, result);
	Merge_Sort(data, (end-start+1)/2+start+1, end,result);
	Merge(data,start,end, result);
	for(int i = start; i <= end; i++)
		data[i] = result[i];
  }
}
void Merge(int *data, int start, int end, int * result)
{
  int left_length =(end -start+1)/2 +1;
  int left_index = start;
  int right_index = start+left_length;
  int result_index = start;
  while(left_index < start+left_length && right_index < end+1)
  {
     if(data[left_index] <= data[right_index])
		 result[result_index++]= data[left_index++];
	 else
		 result[result_index++]= data[right_index++];
  }
  while(left_index < start + left_length)
	  result[result_index++] = data[left_index++];
  while(right_index < end +1)
	  result[result_index++] = data[right_index++];

}
int main()
 {
	 int data[] = {3,4,5,12,2,1};
	 const int length = sizeof(data) / sizeof(data[0]);
	 int result[length] = {0};
	 cout << "Befor Sort: " <<endl;
	 for(int i = 0; i < length; i++)
		 cout << data[i] << " ";
	 cout << endl;
	 cout << "排序後： "<<endl;
	 Merge_Sort(data, 0, length-1, result);
	 for(int i = 0; i < length; i++)
		 cout << data[i] << " ";
	     cout <<endl;
	 return 0;

}