SMMR-238: Surprise Gift

#include <bits/stdc++.h> // include everything
using namespace std;

/*
STAFF'S FUNCTIONS
*/

struct Node {
    int val;
    Node *next;
};

int get_list_size(Node* head) {
    return head == NULL ? 0 : 1 + get_list_size(head->next);
}

void print_list(Node* head) {
    if (head == NULL)
        return;
    printf("%d ", head->val);
    print_list(head->next);
}

Node* insert_front(Node* head, int val) {
    Node* new_node = new Node; // same as malloc(sizeof(Node))
    new_node->val = val;
    new_node->next = head;
    return new_node;
}

Node* free_list(Node* head) {
    if (head != NULL) {
        free_list(head->next);
        delete head; // same as free(head)
    }
    return NULL;
}

/*
STUDENT'S FUNCTIONS
*/

Node* get_tail(Node* head) {
    // your code here
    if(head -> next == nullptr) return head;
    head = get_tail(head -> next);
    return head;
}

Node* split_at_k(Node* head, int k) {
    // your code here
    if(k == 1){
        Node *cur = head -> next;
        head -> next = nullptr;
        return cur;
    }
    head = split_at_k(head -> next, k-1);
    return head;
}

Node* flip_chunks_of_two(Node* head) {
    // your code here
    if(head == nullptr) return nullptr;
    if(head -> next == nullptr) return head;
    Node *a, *b, *c;
    a = head;
    b = head -> next;
    c = head -> next -> next;
    b -> next = a;
    a -> next = flip_chunks_of_two(c);
    return b;
}

/*
STAFF'S MAIN
*/

void print_list_addresses(Node* head) {
    if (head == NULL)
        return;
    printf("%p ", head);
    print_list_addresses(head->next);
}

void print_list(Node* head, const char* name) {
    printf("%s\n", name);
    print_list(head);
    printf("\n");
    print_list_addresses(head);
    printf("\n");
}

int main()
{
    // build input list
    int n, q;
    scanf("%d%d", &n, &q);
    int input[n];
    for (int i = 0; i < n; ++i)
        scanf("%d", &input[i]);
    Node* head = NULL;
    for (int i = n-1; i >= 0; --i)
        head = insert_front(head, input[i]);
    print_list(head, "Before: Input");

    if (q == 1) {
        Node* tail = get_tail(head);
        print_list(tail, "After: Tail node");
    } else if (q == 2) {
        int k; scanf("%d", &k);
        Node* sec2 = split_at_k(head, k);
        print_list(head, "After: Front list");
        print_list(sec2, "After: Back list");
    } else if (q == 3) {
        Node* newhead = flip_chunks_of_two(head);
        print_list(newhead, "After: Flipped pairs");
    }

    return 0;
}