C语言-排序-归并排序

思想：运用分治法思想解决排序问题。

void Merge(int A[],int low,int mid,int high)
 {
     int i,j,k;
     int *P = new int[mid-low+1],*Q = new int[high-mid];      

     for (i =0;i  < mid - low +1;++i)   P[i] = A[i+low];

     for (i = 0; i  < high - mid;++i)   Q[i] = A[mid+1+i];      

     i = j = 0,k = low;
     while ((i  <= mid-low) && (j  <= high-mid-1))
     {      

         if (P[i]  <= Q[j])   A[k++] = P[i++];
         else  A[k++]= Q[j++];
     }      

     if (i > mid - low)   { for (;j  <= high-mid-1;++j)   A[k++] = Q[j]; }
     else
     {   for (; i <= mid - low;++i)   A[k++] = P[i];  }      

     delete [] P;
     delete [] Q;
 }      

 void mergeSort(int A[],int left,int right)
 {
     if (left  < right)
     {
         int i = (left + right) / 2;
         MergeSort(A,left,i);
         MergeSort(A,i+1,right);
         Merge(A,left,i,right);
     }
 }