STL:原地归并排序模板（InplaceMergeSort）

原理：就是在归并排序上改进，以时间复杂度换空间复杂度，利用元素反转完成排序

具体过程如下：

具体操作看代码吧，应该没什么难度，主要是reverse要反转三次

 typedef int Position;

 void Merge_Sort(Position, Position, int *const, Position *);
 void Merge(Position, Position, int *const, Position *);
 void Convert(Position, Position, Position, Position *);
 void Reverse(Position, Position, Position *);
 void Swap(Position *, Position, Position);

 void Merge_Sort(Position Left, Position Right, int *const Inverse_Num, Position *A)
 {
     if (Left < Right)
     {
         Position Mid = (Left + Right) / ;
         Merge_Sort(Left, Mid, Inverse_Num,A);
         Merge_Sort(Mid + , Right, Inverse_Num,A);
         Merge(Left, Right, Inverse_Num, A);
     }
 }

 void Merge(Position Left, Position Right, int *const Inverse_Num, Position *A)
 {
     Position Mid = (Left + Right) / , lpos = Left, rpos = Mid + , pos = Left, index = rpos;

     while (lpos <= Mid && rpos <= Right)
     {
         while (lpos < rpos && A[lpos] <= A[rpos])
             lpos++;
         index = rpos;
         while (rpos <= Right && A[rpos] < A[lpos])
             rpos++;
         Convert(lpos, index - , rpos - , A);
         lpos += rpos - index;
     }
 }

 void Convert(Position Left, Position Mid, Position Right, Position *A)
 {
     Reverse(Left, Mid, A);
     Reverse(Mid + , Right, A);
     Reverse(Left, Right, A);
 }

 void Reverse(Position Left, Position Right, Position *A)
 {
     Position i = Left, j = Right;
     while (i < j)
         Swap(A, i++, j--);
 }

 void Swap(Position *A, Position i, Position j)
 {
     A[i] ^= A[j];
     A[j] ^= A[i];
     A[i] ^= A[j];
 }

参考：http://blog.csdn.net/acdreamers/article/details/24244643