list.c

#include <stdio.h>
#include <stdlib.h>
#include "list_2.h"

struct nodo{
    int key;
    link pred, next;
};

void swap(list l, int k){
    int i = 0, tmp;
    link h = l.head;
    link t = l.tail;
    if(k < 0) //aggiunto controllo
        return;
    if(h == NULL)
        return;
    for( ; i < k ; t = t->pred, h =  h->next){
        if(t == h)
            return;
        i++;
    }
    tmp = h->key;
    h->key = t->key;
    t->key = tmp;
}

void initList(list *l){
    l->tail = NULL;
    l->head = NULL;

}

void insertHead(list *l, int val){
    if(l->head == NULL){
        l->head = malloc(sizeof(struct nodo));
        l->head->pred = NULL;
        l->head->key = val;
        l->head->next = NULL;
        l->tail = l->head;
        return;
    }
    link x = malloc(sizeof(link *));
    if(x == NULL){
        printf("errore nell'allocazione del nodo\n");
        return;
    }
    x->key = val;
    x->pred = NULL;
    x->next = l->head;
    l->head->pred = x;
    l->head = x;
}


void insertTail(list *l, int val){
    if(l->tail == NULL){
        l->head = malloc(sizeof(struct nodo));
        l->head->pred = NULL;
        l->head->key = val;
        l->head->next = NULL;
        l->tail = l->head;
        return;
    }
    link x = malloc(sizeof(link *));
    if(x == NULL){
        printf("errore nell'allocazione del nodo\n");
        return;
    }
    x->key = val;
    x->pred = l->tail;
    x->next = NULL;
    l->tail->next = x;
    l->tail = x;
}



void delKey(list *l, int k){
    link x = l->head;
    link y;
    if(x == NULL)
        return;

    for( ; x != NULL ; y = x, x = x->next){
        if(x->key == k){
            if(x == l->head){
                l->head = l->head->next;
                free(x);
                return;
            }
            if(x == l->tail){
                l->tail = l->tail->pred;
                free(x);
                return;
            }
            y->next = x->next;
            x->next->pred = x->pred;
            free(x);
            return;
        }
    }

}

void printList(FILE *fp, list *l){
    link x = l->head;
    if(x == NULL)
        return;
    for( ; x != NULL ; x = x->next)
        printf(" %d ", x->key);
    printf("\n");
}