Need guidance on Binary Radix Sort in C

Question

This is what i have so far but its not giving me the output i want. I need the array that the user will fill be sorted by using bitwise operations in the radix sort function. The instructions for this states that i should use the bitwise operations to extract the bits and then use the value of the bits as the bucket indexes.

void radix_sort(unsigned int *array, int num, int bits);

int main()
{   
    int bits = 32;
    int num = 0;
    
    printf("Enter number of elements: ");
    scanf("%d", &num);
    
    unsigned int array[100];
    
    if(num > 100)
    {
        printf("Number of elements cannot be greater than 100.");
    }
    else
    {
        for(int i = 0; i < num; i++)
        {   
            unsigned int elem;
            printf("Enter a number: ");
            scanf("%u", &array[i]);
            //array[i] = elem;
            //printf("%d\n", array[i]);
        }
    }
    
    radix_sort(array, num, bits);
    for(int i = 0; i < num; i++)
    {
        printf("%u\n", array[i]);
    }
    return 0;
}


void radix_sort(unsigned int *array, int num, int bits)
{
    unsigned int bucket_0[num];
    unsigned int bucket_1[num];
    
    for(int d = 0; d < bits; d++)
    {   
        int count0 = 0;
        int count1 = 0;
        for(int i = 0; i < num; i++)
        {
            if( ( array[d] & (1 >> i) ) != 0)
            {
                bucket_1[i] = array[d];
                count1++;
            }
            else
            {
                bucket_0[i]= array[d];
                count0++;
            }
        }
        
        int i = 0;
        for(int j = 0; j < count0; ++i, ++j)
        {
            array[i] = bucket_0[j];
            //printf("%d\n",bucket_0[j]);
        }
        
        for(int j = 0; j < count1; ++i, ++j)
        {
            array[i] = bucket_1[j];
        }
    }
    
}

Answer 1

Couple of obvious typo errors:

• when putting elements into the buckets, you should use bucket_1[count1] = array[i] and bucket_0[count0] = array[i] rather than what you have

• you've swapped i and d in a number of places

• 1 >> i will be 0 when i > 0 -- you want 1 << d instead.