对于非常大的输入文件数据,此排序代码会失败,因为它需要很长时间才能完成。
rewind(ptr);
j=0;
while(( fread(&temp,sizeof(temp),1,ptr)==1) &&( j!=lines-1)) //read object by object
{
i=j+1;
while(fread(&temp1,sizeof(temp),1,ptr)==1) //read next object , to compare previous object with next object
{
if(temp.key > temp1.key) //compare key value of object
{
temp2=temp; //if you don't want to change records and just want to change keys use three statements temp2.key =temp.key;
temp=temp1;
temp1=temp2;
fseek(ptr,j*sizeof(temp),0); //move stream to overwrite
fwrite(&temp,sizeof(temp),1,ptr); //you can avoid above swap by changing &temp to &temp1
fseek(ptr,i*sizeof(temp),0); //move stream to overwrite
fwrite(&temp1,sizeof(temp),1,ptr); //you can avoid above swap by changing &temp1 to &temp
}
i++;
}
j++;
fseek(ptr,j*sizeof(temp),0);
}
知道如何让这个 C 代码更快吗?也会使用qsort()
(在 C 中预定义)要快得多,应该如何应用于上面的代码?