lista cykl. - usuwanie parzystych

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

typedef struct tnode
{
    int value;
    struct tnode *next;
} tnode;


tnode *add(tnode *list_1, tnode *list_2)
{
    tnode *hold=list_1;
    if (hold==NULL)
    {
        list_2->next=list_2;
        return list_2;
    }
    else
    {
        tnode *current_1=list_1;
        while(current_1->next!=hold)
        {
            current_1=current_1->next;
        }

        current_1->next=list_2;
        list_2->next=hold;

        return hold;
    }
}

void wypisz_cycle ( tnode *list)
{
    if (list == NULL)
    {
        printf ("PUSTA \n");
        return;
    }
    tnode * wsk = list;
    do
    {
        printf ("[%d]  ", list->value);
        list = list->next;
    }
    while (list != wsk);
    return;
}

void wypisz(tnode *list)
{
    if (list==NULL)
        return;
    while (list!=NULL)
    {
        printf("[%d]->",list->value);
        list=list->next;
    }
    puts("\n");
}

void usun(tnode **list)
{
    if ((*list)==NULL)
        return;
    tnode *head=*list;
    tnode *last=*list;
    while (last->next!=head)
        last=last->next;
    last->next=NULL;

    while ((head->value)%2==0 && head!=NULL)
    {
        tnode *tmp=head;
        head=head->next;
        free(tmp);
    }
    *list=head;

    if(head==NULL)
    {
        return;
    }

    tnode *current=*list;
    tnode *prev=*list;
    current=current->next;
    while(current!=NULL)
    {
        if((current->value)%2==0)
        {
            current=current->next;
            free(prev->next);
            prev->next=current;
        }
        else
        {
            current=current->next;
            prev=prev->next;
        }
    }

}

int main()
{
    tnode *head=NULL;
    tnode *one=malloc(sizeof(tnode));
    tnode *two=malloc(sizeof(tnode));
    tnode *three=malloc(sizeof(tnode));
    tnode *four=malloc(sizeof(tnode));
    one->value=2;
    one->next=NULL;
    two->value=3;
    two->next=NULL;
    three->value=4;
    three->next=NULL;
    four->value=5;
    four->next=NULL;

    head=add(head,one);
    head=add(head,two);
    head=add(head,three);
    head=add(head,four);
    puts("Pierwsza lista:");
    wypisz_cycle(head);
    printf("lista1 = %d, lista2 = %d\n",head->value,head->next->value);
    usun(&head);
    //wypisz_cycle(head);
    wypisz(head);
    return 0;
}