I'm trying to come up with a rudimentary radix sort (I've never actually seen one, so I'm sorry if mine is awful), but I am getting an EXC_BAD_ACCESS
error on the line link = *(link.pointer);
. My C
skills aren't great, so hopefully someone can teach me what I'm doing wrong.
I'm using XCode and ARC is enabled.
Here is the code:
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <time.h>
#define ARRAY_COUNT 10
#define MAX_VALUE 1000000
#define MODULO 10.0f
typedef enum
{
false,
true
} bool;
typedef struct linkedListStruct
{
int value;
struct linkedListStruct *pointer;
} LinkedList;
void radixSort(int *array);
bool arraySorted(int *array);
int * intArray(int minValue, int maxValue);
int main(int argc, const char * argv[])
{
int *sortingArray = intArray(0, MAX_VALUE);
radixSort(sortingArray);
printf("Array %s sorted", arraySorted(sortingArray) ? "" : "not");
return 0;
}
void radixSort(int *array)
{
int numberOfIterations = (int)ceilf(log(MAX_VALUE)/log(MODULO));
for(int n = 0; n < numberOfIterations; n++)
{
LinkedList *linkedListPointers[(int)MODULO] = {0};
int i = ARRAY_COUNT;
while(i--)
{
int location = (int)floor((array[i] % (int)powf(MODULO, n + 1))/powf(MODULO, n));
LinkedList link = { array[i], NULL };
link.pointer = linkedListPointers[location];
linkedListPointers[location] = &link;
}
int location = 0;
for(int pointerSelection = 0; pointerSelection < MODULO; pointerSelection++)
{
if(linkedListPointers[pointerSelection])
{
LinkedList link = { 0, linkedListPointers[pointerSelection] };
linkedListPointers[pointerSelection] = NULL;
while(link.pointer)
{
link = *(link.pointer);
array[location++] = link.value;
}
}
}
}
}
bool arraySorted(int *array)
{
int i = ARRAY_COUNT;
while(--i)if(array[i - 1] > array[i])break;
return !i;
}
int * intArray(int minValue, int maxValue)
{
int difference = maxValue - minValue;
int *array = (int *)malloc(sizeof(int) * ARRAY_COUNT);
int i;
for(i = 0; i < ARRAY_COUNT; i++)
{
array[i] = rand()%difference + minValue;
}
return array;
}
Also, if someone wants to suggest improvements to my sort, that would also be appreciated.
The problem came from how I was allocating the linked list. I changed
LinkedList link = { array[i], NULL };
link.pointer = linkedListPointers[location];
to
LinkedList *link = malloc(sizeof(LinkedList));
link->value = array[i];
link->pointer = linkedListPointers[location];
In the first example, the pointer to link
remained the same through each loop iteration (I wasn't aware it would do that), so I needed to make the pointer point to a newly allocated memory chunk.
EDIT:
Changing that also had me change from
while(link.pointer)
{
link = *(link.pointer);
array[location++] = link.value;
}
to
while(linkPointer)
{
link = *linkPointer;
array[location++] = link.value;
linkPointer = link.pointer;
}
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