lsort/radix.c

#include "include/types.h"
#include "include/radix.h"

static int _seperate_pos_neg(lsort_array_i* array, lsort_array_i* pos_array, lsort_array_i* neg_array) {
    for (int i = 0; i < array->count; i++) {
        if ((0x80000000 & array->items[i]) == 0x80000000) {
            lsort_array_i_append(neg_array, array->items[i]);
        } else {
            lsort_array_i_append(pos_array, array->items[i]);
        }
    }
    return 0;
}

static int _sort_items(lsort_array_i* numbers, lsort_array_i_array* buckets) {
    int byte_check = 0x0000000F;

    for (int i = 0; i < 8; i++) {
        // Loop through the list of numbers and append them to their respective buckets for this 4-byte chunk
        for (int item_index = 0; item_index < numbers->count; item_index++) {
            int* current_number = &numbers->items[item_index];
            lsort_array_i* bucket = buckets->items[(*current_number >> (i * 4)) & byte_check];

            lsort_array_i_append(bucket, *current_number);
        }
        
        numbers->count = 0;
        
        // Add the bucketed numbers back to the original array after emptying it
        for (int bucket_number = 0; bucket_number < buckets->count; bucket_number++) {
            lsort_array_i* bucket = buckets->items[bucket_number];

            for (int bucket_item = 0; bucket_item < bucket->count; bucket_item++) {
                lsort_array_i_append(numbers, bucket->items[bucket_item]);
            }

            bucket->count = 0;
        }

        // Repeat for each 4-byte chunk...
    }

    return 0;
}

int lsort_radix(lsort_array_i* array, lsort_array_i* return_array) {
    if (array->count <= 0) return 1;

    // Seperate positive and negative numbers
    lsort_array_i positive_numbers = {0};
    lsort_array_i negative_numbers = {0};
    
    if (_seperate_pos_neg(array, &positive_numbers, &negative_numbers)) return 2;

    // Create buckets
    lsort_array_i_array buckets = {0};
    for (int i = 0; i < 16; i++) {
        lsort_array_i* bucket = lsort_array_i_create();
        lsort_array_i_array_append(&buckets, bucket);
    }

    // Sort each set of numbers using those buckets
    _sort_items(&negative_numbers, &buckets);
    _sort_items(&positive_numbers, &buckets);
    
    // Add each array of numbers to the return array
    for (int i = 0; i < negative_numbers.count; i++) {
        lsort_array_i_append(return_array, negative_numbers.items[i]);
    }

    for (int i = 0; i < positive_numbers.count; i++) {
        lsort_array_i_append(return_array, positive_numbers.items[i]);
    }

    // Destroy the buckets
    lsort_array_i_array_destroy(&buckets);

    return 0;
}