List

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

 typedef struct Element {
   struct element *next;
   int val;
 } Element;

 typedef struct List {
    struct Element *first;
    struct Element *current;
    int size;
 } List;
 typedef struct Iterator {
    struct Element *current;
    int size;
 } Iterator;
List* newList() {
    List *lista = malloc(sizeof(List));
    lista->first = malloc(sizeof(Element));
    lista->current = lista->first;
    lista->size = 0;
    return lista;
}
Iterator* newIterator(List *lista) {
    Iterator *iter = malloc(sizeof(Iterator));
    iter->current = lista->first;
    iter->size = lista->size;
}
int hasNext(Iterator *iter) {
    return iter->size > 0;
}

int next(Iterator *iter) {
    iter->size--;
    int val = iter->current->val;
    iter->current = iter->current->next;
    return val;
}

void freeList(List *lista) {
    int i = lista->size-1;
    Element *item = lista->first;
    while (i > 0) {
        Element *temp = item;
        item = temp->next;
        free(temp);
        i--;
    }
    free(lista);
}

void addInt(List *lista, int val) {
    Element *current = lista->current;
    current->val = val;
    current->next = malloc(sizeof(Element));
    lista->current = current->next;
    lista->size++;
}

void addIntAt(List *lista, int val, int index) {
    if (index == lista->size) {
        addInt(lista, val);
    }
    else if (index == 0) {
        Element* oldFirst = lista->first;
        lista->first = malloc(sizeof(Element));
        lista->first->next = oldFirst;
        lista->first->val = val;
        lista->size++;
    }
    else {
        int i = index;
        Element *item = lista->first;
        while (i > 1) {
            item = item->next;
            i--;
        }
        Element* next = item->next;
        Element* newNext = malloc(sizeof(Element));
        item->next = newNext;
        newNext->next = next;
        newNext->val = val;
        lista->size++;
    }

}

int removeIntAt(List *lista, int index) {
    if (index >= lista->size) return ;
    if (index == 0) {
        Element *first = lista->first;
        Element *toRemove = first;
        lista->first = first->next;
        lista->size--;
        int toReturn = toRemove->val;
        free(toRemove);
        return toReturn;
    }
    int i = index;
    Element *item = lista->first;
    while (i > 1) {
        item = item->next;
        i--;
    }
    if (index == lista->size - 1) {
        lista->size--;
        Element *current = lista->current;
        int toReturn = current->val;
        lista->current = item->next;
        return toReturn;
    }
    Element *item1 = lista->first;
    i = index;
    while (i > -1) {
        item1 = item1->next;
        i--;
    }
    Element *toRemove = item->next;
    item->next = item1;
    lista->size--;
    int toReturn = toRemove->val;
    free(toRemove);
    return toReturn;
}

void removeInt(List* lista, int val) {
    Iterator* iter = newIterator(lista);
    int i = 0;
    while(hasNext(iter)) {
        int v = next(iter);
        if (v == val) removeIntAt(lista, i);
        i++;
    }
    free(iter);
}

int containsInt(List* lista, int val) {
    Iterator* iter = newIterator(lista);
    int i = 0;
    while(hasNext(iter)) {
        int v = next(iter);
        if (v == val) {
            free(iter);
            return 1;
        }
        i++;
    }
    free(iter);
    return 0;
}

int getInt(List *lista, int index) {
    if (index >= lista->size) return NULL;
    int i = index;
    Element *item = lista->first;
    while (i > 0) {
        item = item->next;
        i--;
    }
    return item->val;
}
void setInt(List *lista, int val, int index) {
    if (index >= lista->size) return ;
    int i = index;
    Element *item = lista->first;
    while (i > 0) {
        item = item->next;
        i--;
    }
    item->val = val;
}

int main() {
    List* lista = newList();
    addInt(lista, 10);//0
    addInt(lista, 20);//1
    addInt(lista, 30);//2
    addInt(lista, 55);//3
    addIntAt(lista, 38, 3);
    setInt(lista, 11, 0);
    removeIntAt(lista, 1);
    Iterator* iter = newIterator(lista);
    while (hasNext(iter)) {
        printf("%d\n", next(iter));
    }
    free(iter);
    freeList(lista);
    return 0;
}