Bubble sort universal implementation in C

问题:

I'm trying to make an universal bubble sort function. It allow to user to write its own compare and swap function. I implemented a swap and compare function for int type, but when I run the code for next array: {3, 5, 8, 9, 1, 2, 4, 7, 6, 0} , I get: 0 0 84214528 2312 1 2 4 7 6 0. Why this is happening?

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

#define true 1
#define false 0

int compInt(void *a, void *b) // FUNCTION FOR COMPARE INT
{
    if (*(int*)(a) > *(int*)(b)) { return false; } // IF FIRST INT > SECOND INT (WRONG ORDER) RETURN FALSE
    return true; // RIGHT ORDER -> RETURN TRUE
}

I think the problem is somewhere in swapInt.

void swapInt(void *a, void *b) // FUNCTION FOR SWAP INT
{
    int aux; // TEMPORARY VARIABLE, IT STORAGES VALUE OF *(int*)(a)

    aux = *(int*)(a);
    *(int*)(a) = *(int*)(b); // a value is now equal to b value
    *(int*)(b) = aux; // b has value of aux
}

void bubbleSort(void *address, int len, int (*comp)(void *a, void *b), void (*swap)(void *a, void *b)) // bubble sort function allow to user to write it's compare and swap function
{
    int newlen;

    while (len != 0) {
        newlen = 0;
        for (int i = 1; i < len; i++) {         
            if (!comp(address + i - 1, address + i)) {
                swap(address + i - 1, address + i);
                newlen = i;  
            }
        }
        len = newlen;
    }
}

int main()
{
    int array[] = {3, 5, 8, 9, 1, 2, 4, 7, 6, 0}; // CREATE AN ARRAY OF INT
    int len = 10; // DECLARE IT LEN

    void *address; // VOID POINTER TO ARRAY
    address = array;

    bubbleSort(address, len, &compInt, &swapInt); // SORT IT 
    for (int i = 0; i < len; ++i) { 
        printf("%d ", array[i]); // PRINT IT
    }

    return 0;
}

Thanks for help!

回答1:

Thanks @mephi42. Here's the update version.

The problem is in your bubbleSort function. You should add the address with the offset multiplied by element size.

The right codes should be:

void bubbleSort(void *address, int len, size_t ele_size, int (*comp)(void *a, void *b), void (*swap)(void *a, void *b)) // bubble sort function allow to user to write it's compare and swap function
{
    int newlen;

    while (len != 0) {
        newlen = 0;
        for (int i = 1; i < len; i++) {         
            if (!comp((char*)address + ele_size * (i - 1), (char*)address + ele_size * i)) {
                swap((char*)address + ele_size * (i - 1), (char*)address + ele_size * i);
                newlen = i;  
            }
        }
        len = newlen;
    }
}

And then call the function like:

bubbleSort(address, len, sizeof(int), compInt, &swapInt);