歸併排序

簡單的歸併排序代碼，C實現

#include<stdio.h>
#include<stdlib.h>


//conquer
void merge(int *A, int left ,int mid, int right)
{
   int i;
   int j;
   int Tl[8];
   int Tr[8];
   int lnum;
   int rnum;

   lnum = mid-left+1;
   rnum = right - mid;

   //assinment 
   for(i =0;i<lnum;i++)
       Tl[i]=A[left+i];
   for(j =0;j<rnum;j++)
       Tr[j] = A[mid+j+1];

   i = 0;
   j =0;


   //assignment the smaller num to sequence-array;
   //and if one temp array(Tr or Tl) is over,
   //transport the rest num of another array to sequence-array 
   while(i<(lnum)&&j<(rnum))
   {
       if(Tl[i]<Tr[j])
           A[left++] = Tl[i++];
       else
           A[left++] = Tr[j++];
   }
   while(i<(lnum))
   {
       A[left++] = Tl[i++];
   }
   while(j<(rnum))
   {
       A[left++] = Tr[j++];
   }
}

//divide
void merge_sort(int *A,int left,int right)
    {
         int mid;
        if(left<right)
        {
            mid = (left+right)/2;
            merge_sort(A,left,mid);
            merge_sort(A,mid+1,right);
            merge(A,left,mid,right);
        }

    }



int main()
{
   //test simply
   int A[8] = {5,4,3,2,1,0,7,6};

   //merge sort
   merge_sort(A,0,7);

   for(int i=0;i<8;i++)
       printf("%d",A[i]);
   system("pause");


}

歸併排序的思想很簡單，但是寫成代碼還是需要小心一點，有很多小細節需要注意，最好的方式是能夠記住一種寫法，這樣可以提高效率。