Radix Sort Base 16 (Hexadecimals)

Question

I have spent more 10hr+ on trying to sort the following(hexadecimals) in LSD radix sort, but no avail. There is very little material on this subject on web.

Answer 1

void int_radix_sort(void) {
    int group; //because extracting 8 bits
    int buckets = 1 << 8; //using size 256
    int map[buckets];   
    int mask = buckets - 1;
    int i;
    int cnt[buckets];
    int flag = NULL;
    int partition;
    int *src, *dst;

    for (group = 0; group < 32; group += 8) {
        // group = 8, number of bits we want per round, we want 4 rounds
        // cnt  
        for (int i = 0; i < buckets; i++) {
            cnt[i] = 0;
        }
        for (int j = 0; j < n; j++) {
            i = (lst[j] >> group) & mask;
            cnt[i]++; 
            tmp[j] = lst[j];
        }

        //map
        map[0] = 0;
        for (int i = 1; i < buckets; i++) {
            map[i] = map[i - 1] + cnt[i - 1];
        }

        //move
        for (int j = 0; j < n; j++) {   
            i = (tmp[j] >> group) & mask;
            lst[map[i]] = tmp[j];
            map[i]++;
        }
    }
}

After hours of researching I came across the answer. I'm still do not understand what is going on in this code/answer. I cannot get my head wrapped around the concept. Hopefully, someone can explain.