#include <stdio.h>
#include <stdlib.h>

struct node {
    int num;
    int occ;
    struct node *next;
    struct node *prev;
};

void printlist(struct node *list_head){
    struct node *iteratore = list_head;
    while (iteratore != NULL){
        printf("{num: %d, occ: %d}->", iteratore->num, iteratore->occ);
        iteratore = iteratore->next;
    }
    printf("\b\b  \n");
    return;
}

struct node *createnode(int x){
    struct node *node = (struct node*)malloc(sizeof(struct node));
    node->num = x;
    node->occ = 1;
    return node;
}

void insertnode(struct node **list_head, int x){

    // inserimento in testa
    if (*list_head == NULL){
        struct node *node = createnode(x);
        node->next = NULL;
        node->prev = NULL;
        *list_head = node;
        return;
    }

    // inserimento in lista
    struct node *iteratore = *list_head;
    struct node *node = createnode(x);
    while(iteratore->next != NULL){
        if (x == iteratore->num){
            iteratore->occ +=1;
            node->occ = iteratore->occ;
        }
        iteratore = iteratore->next;
    }
    node->next = NULL;
    node->prev = iteratore;
    iteratore->next = node;
    return;
}

struct node *list(int n, int A[n]){
    struct node *list_head = NULL;

    int i;
    for (i = 0; i < n; i++){
        insertnode(&list_head, A[i]);
    }

    return list_head;
}

void reverse(struct node **list_head){

    if (*list_head == NULL){
        printf ("Lista vuota!");
        return;
    }

    struct node *iteratore = *list_head;
    while (iteratore->next != NULL){
        struct node *temp = iteratore->next;

        // reversing list head
        if (iteratore == *list_head){
            iteratore->prev = iteratore->next;
            iteratore->next = NULL;
        }
        else{
            struct node *app = iteratore->prev;
            iteratore->prev = iteratore->next;
            iteratore->next = app;
        }
        iteratore = iteratore->prev;

    }

    iteratore->next = iteratore->prev;
    iteratore->prev = NULL;
    *list_head = iteratore;
    return;
}

int main(void){

    int n = 7;
    int array[7] = {2,7,8,2,1,5,2};

    struct node *list_head;
    list_head = list(n, array);
    printlist(list_head);

    reverse(&list_head);
    printlist(list_head);

    return 0;
}