CODEWITHSUNDEEP
cunixsortingquicksortstruct
Viktor Jagar
Viktor Jagar

Reputation: 26

Attempting to implement quicksort in c - sorting structs

Having a little trouble with my quicksort - I'm attempting to pass it & but keep doing something wrong. Any insight would be greatly appreciated.

The code is implementing a generic quicksort that I found online. Essentially, I'm attempting to copy it but sort by the struct's distance. Therefore if the distance is smaller - I want to move the two files and sort them appropriately.

Thanks!

typedef struct Tag 
{
    char classify;
    float pointX;
    float  pointY;
    float distance;
}PointClassify;

void swap(PointClassify &i, PointClassify &j) 
{
    PointClassify temp;
    temp = i;
    i = j;
    j = temp;
}
void quickSort(PointClassify item[], int start, int end)
{
    float pivot;
    int i = start, j = end;

    pivot = item[(start+end)/2].distance;

    while(i <= j)
    {   
            while(item[i].distance < pivot)
            {   
                    i = i+1;
            }   
            while(item[j].distance > pivot)
            {   
                    j = j-1;
            }   
            if(i <= j)
            {   
                    swap(item[i],item[j]);
                    i = i+1;
                    j = j-1;
            }   
     }   
 fprintf(stderr, "This is the number %d \n", item[i].distance);
    if(start < j)
    {   
            quickSort(item, start, j); 
    }   
    if(i < end)
    {   
            quickSort(item, i, end);
    }   
}

Upvotes: 1

Views: 794

Answers (2)

Karoly Horvath
Karoly Horvath

Reputation: 96316

Does it not compile?

pass-by-reference is a C++ feature. Use pointers:

swap(PointClassify *i, PointClassify *j)

Upvotes: 1

Christopher Neylan
Christopher Neylan

Reputation: 8292

Change this:

void swap(PointClassify &i, PointClassify &j)

to this:

void swap(PointClassify *i, PointClassify *j)

In C, in a declaration, the * indicates that the variable is a pointer to something of that type. You use the & operator to take the address of a varaible. You would use it when calling the function, for example:

swap(&item[i], &item[j]);

Upvotes: 2

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