用通用大小对结构数组进行排序

Question

I am new to C and I guess my code is far away of best practice..

I have an Array of struct in my C programm. The size of the array is 255 (allocated) but not all of it is used.

the Array in my eample is filled with following vaues:

2;a;121212;121212;0
9;c;121212;121212;1
6;d;121212;121212;1
4;e;121212;121212;1
1;v;121212;121212;1
8;x;121212;121212;1

the rest is filled with null values.. (I guess)

Now my problem is not with the actual sorting. It's when I start sorting, it will come to the point of taking an empty Index of my Array and faulting.

the array of books:

struct book{
    int ID;
    char name[MAX_STR_LEN];
    char dateIn[DATE_LEN];
    char dateOut[DATE_LEN];
    int isIn;
};


/* array of my books */
struct book books[MAX_BOOKS];

The sorting function:

void sort()
{
    /* first find out how many indexes there are */
    int h;
    for (h = 0; h< MAX_BOOKS; h++)
    {
        if (books[h].ID == 0)
        {
            break;
        }
    }

    int j =  0;

    int swaped = 1;
    struct book temp;
    while (swaped == 1)       //bubble sort on the book name
    {
        for(j=0;j< h ;j++)
        {
            swaped = 0;
            if(strcmp(books[j].name,books[j + 1].name)>0)
            {

                //copy to temp val
                temp.ID = books[j].ID;
                strcpy(temp.name,books[j].name);
                strcpy(temp.dateIn,books[j].dateIn);
                strcpy(temp.dateOut,books[j].dateOut);
                temp.isIn = books[j].isIn;


                //copy next val
                books[j].ID = books[j + 1].ID;
                strcpy(books[j].name,books[j + 1].name);
                strcpy(books[j].dateIn,books[j + 1].dateIn);
                strcpy(books[j].dateOut,books[j + 1].dateOut);
                books[j].isIn = books[j + 1].isIn;


                //copy back temp val
                books[j + 1].ID = temp.ID;
                strcpy(books[j+ 1].name,temp.name);
                strcpy(books[j + 1].dateIn,temp.dateIn);
                strcpy(books[j + 1].dateOut,temp.dateOut);
                books[j + 1].isIn = temp.isIn;


                swaped = 1;

            }
        }
    }

}

So my question would be if its possible to sort only values with where the ID is not 0?

If you need more information, I will try to deliver..

Thanks in advance!

Answer 1

for(j=0;j< h ;j++)
{
    if(strcmp(books[j].name,books[j + 1].name)>0)
    {

Here you are taking j from 0 to h-1 , inclusive. So you are trying to compare for j == h-1 the last element books[j] with the next one books[j+1] , which does not exist. You probably only want to check up to the pair h-2 / h-1 , that is for(j=0; j<h-1; j++) .

Answer 2

Why you are doing such big calculation for swaping? why dont you just do

if(strcmp(books[j].name,books[j + 1].name)>0){

   temp = books[j];
   books[j] = books[j+1];
   books[j+1] = temp;
} 

And it is possible to sort your structure array. If you are able to do swaping on struct then you can do any kind of sorting algorithm.

change this condition if(strcmp(books[j].name,books[j + 1].name)>0) to if(books[j].ID>books[j + 1].id) then you can sort the struct with respect to ID .

But follow the @Nabla's answer too.

Answer 3

Nabla's answer is right. Also, you set swapped = 0; at the wrong place. You have:

while (swapped == 1)       //bubble sort on the book name
{
    for (j = 0; j < h; j++)
    {
        swapped = 0;

but you want:

while (swapped == 1)       //bubble sort on the book name
{
    swapped = 0;
    for (j = 0; j < h; j++)
    {