Solution to problem Cartas

// Solution to problem Cartas by dacanizares
#include <bits/stdc++.h>

using namespace std;

struct Node{
    int value;
    Node* next;
    Node* prev;

    Node(int v){
        value = v;
        next = nullptr;
        prev = nullptr;
    }
};

struct List{
    int count;
    Node* first;
    Node* last;

    void add(int v){
        Node* n = new Node(v);
        if(first == nullptr){
            n->next = n;
            n->prev = n;

            first = n;
            last = n;
        } else{
            n->prev = last;
            n->next = first;

            last->next = n;
            first->prev = n;

            last = n;
        }

        ++count;
    }

    void debug(){
        Node* n = first;
        for(int i = 0; i < count; ++i){
            cout << "["<< n->prev->value << "|" << n->value << "|" << n->next->value <<"] ";
            n = n->next;
        }
        cout << '\n';
    }

    void del(Node* n){
        if(count == 0)
            return;

        if(count == 1){
            first = nullptr;
            last = nullptr;
        } else {
            n->next->prev = n->prev;
            n->prev->next = n->next;

            if(n == first){
                first = n->next;
            }
            if (n == last){
                last = n->prev;
            }
        }

        delete n;
        --count;
    }

    List(){
        count = 0;
        first = nullptr;
        last = nullptr;
    }
};

// Some fast-coded unit test
void tests(){
    // Inserting
    List l;
    l.add(1);
    l.add(2);
    l.add(3);

    l.debug();
    assert(l.count == 3);

    // Deleting first
    l.del(l.first);
    l.debug();
    assert(l.first->value == 2);
    assert(l.count == 2);
    assert(l.first->next == l.last);
    assert(l.first->prev == l.last);
    assert(l.last->next == l.first);

    // Deleting last
    l.del(l.last);
    l.debug();
    assert(l.last->value == 2);
    assert(l.count == 1);
    assert(l.first->next == l.last);
    assert(l.first->prev == l.last);
    assert(l.last->next == l.first);

    // Adding after deleting
    l.add(6);
    l.debug();
    assert(l.last->value == 6);
    assert(l.count == 2);
    assert(l.first->next == l.last);
    assert(l.first->prev == l.last);
    assert(l.last->next == l.first);

    // Deleting all
    l.del(l.first);
    l.del(l.first);
    assert(l.first == nullptr);

    // Adding
    l.add(1);
    l.debug();
    assert(l.last->value == 1);
    assert(l.count == 1);
    assert(l.first->next == l.last);
    assert(l.first->prev == l.last);
    assert(l.last->next == l.first);
}

// Prints the answer
void print(List *l){
    Node* cur = l->first;
    for(int i = 0; i < l->count; ++i){
        switch(cur->value){
            case 1: cout << 'A'; break;
            case 10: cout << 'J'; break;
            case 11: cout << 'Q'; break;
            case 12: cout << 'K'; break;
            default: cout << cur->value; break;

        }

        cout << " ";

        cur = cur->next;
    }
}

int main(){
    //tests();

    int n, k, t;
    while(cin >> n >> k >> t){
        List l;
        for(int i = 0; i < n; ++i){
            l.add(k);

            k++;
            if(k == 13) k = 1;
        }

        Node* top = l.first;
        Node* bot = l.last;
        for(int i = 0; i < (n + 1) / 2; ++i){
            if(t == 1){
                swap(top->value, top->next->value);
                top = top->next->next;
            } else {
                swap(top->value, bot->value);
                top = top->next;
                bot = bot->prev;
            }
        }

        List l2;
        Node* cur = l.first;
        Node* next;
        for(int i = 0; i < n; ++i){
            next = cur->next;
            if(t == 1){
                if((i+1) % 2 == 0 && cur->value % 2 == 0){
                    l2.add(cur->value);
                    l.del(cur);
                }
            } else {
                if((i+1) % 2 != 0 && cur->value % 2 != 0){
                    l2.add(cur->value);
                    l.del(cur);
                }
            }
            cur = next;
        }

        print(&l);
        print(&l2);
        cout << '\n';
    }
    return 0;

}