Bucket Sort Seg Fault - c

Question

I'm trying to implement a bucket sort using a resizable vector function that I made. The vector works fine, but I get a segmentation fault anytime I try to run my sort function. Can anyone help me remedy this?
Notes about code: K=# of buckets in this case 10. find_max and find_min do exactly what you'd expect. vector_int_construct initializes an array and vector_int_push_back pushes integers to the end of the array. vector_int_sort just calls on a merge_sort function I created that also works fine on its own.
typedef struct {
size_t size;
size_t maxsize;
int* array;
}
vector_int_t;
void bucket_sort( int* a, size_t size )
{
int min = find_min( a, size );
int max = find_max( a, size );
size_t range = (( max - min ) / K );
vector_int_t buckets[K];
for( size_t i = 0; i < K; i++ ) {
vector_int_construct( &buckets[i] );
for( size_t j = 0; j < range; j++ ) {
vector_int_push_back( &buckets[i], a[j] );
}
}
for( size_t i = 0; i < K; i++ ) {
vector_int_sort( &buckets[i] );
}
size_t cnt = 0;
while( cnt != size ) {
for( size_t i = 0; i < K; i++ ) {
for( size_t j = 0; j < vector_int_size( &buckets[i] ); j++ ) {
a[cnt] = buckets[i].array[j];
cnt++;
}
}
}
}
int main()
{
size_t size = 4;
int a[] = { 19, 95, 4, 23 };
// Print out array before
printf( "Before sorting: " );
ece2400_print_array( a, size );
// Call sort
bucket_sort( a, size );
// Print out array after
printf( "After sorting: " );
ece2400_print_array( a, size );
return 0;
}