Structures in C : Implementing Linked list using an array

Question

In this program, I'm trying to implement a linked list using an array. I initialised the elements of the array tabList to -1 so that I can consider every element of the array whose value is -1 as an empty box that i can use to store a new element in the list.

I am getting segmentation error when trying to run this program. Can you explain please what is the error in my code

I tried to debug my code, It says that there's an error in line 75 : while(list.tabList[i].valeurElem != -1)

Here is my code :

typedef struct elementList
{
    int valeurElem;
    int indexSuivant;
    int indexElem;

} elementList;


typedef struct list{

    elementList tabList[tailleMax];
    int debut;
    int fin;

} listT;

// To initialize the list 
void initListT(listT list)
{

for(int i = 0; i < tailleMax; i++)
   {
        list.tabList[i].valeurElem      = -1;
        list.tabList[i].indexSuivant    = -1;
        list.tabList[i].indexElem       = -1;

   }

}

// To create a new linked list
listT creerListeT()
{
    listT alist;

    initListT(alist);
    alist.debut = 0;
    alist.fin   = 0;

   return alist;
}


// To test if the list is empty
bool estVideListT(listT list)
{
    return list.tabList[ 0 ].valeurElem   ==  -1 ; 
}

// Function To insert in the head of the linked list 
listT insererTeteListT(listT list, int elemInserer)
{
    if( estVideListT(list) )
    {
        int a = list.debut;
        list.tabList[ a ].valeurElem     = elemInserer;
        list.tabList[ a ].indexSuivant   = list.debut + 1;
        list.tabList[ a ].indexElem      = list.debut;

        return list;
    }
    else 
    {
        int i = 0;

    while(list.tabList[i].valeurElem != -1)
    {
        i++;
    }

    list.tabList[ i ].valeurElem   = elemInserer;
    list.tabList[ i ].indexSuivant = list.debut;
    list.debut = i;

    return list;
    }

}



void printList(listT list)
{
    if( estVideListT(list) )  // testing if the array is empty
    {
        printf("The array is empty\n");
    }
    else
    {
        int i = list.debut;

        while( list.tabList[i].indexSuivant != -1 )
        {
            printf("Element with index %d is : %d \n", i, list.tabList[i].valeurElem);
            i++;
        }

    printf("Element with index %d (Last element) is : %d \n", i, list.tabList[i].valeurElem);

    }
}

int main()
{
    // Creating the list
    listT myList =  creerListeT();

    // Insertion of the elements in the list (each element in the head of the list)
    insererTeteListT(myList, 5);
    insererTeteListT(myList, 3);
    insererTeteListT(myList, 2);
    insererTeteListT(myList, 4);
    insererTeteListT(myList, 7);

    // Printing the list 
    printList(myList);

    return 0;
}

Answer 1

here is a working example as per to your base-code, Do not forget to release the memory corresponding to malloc. I will leave that as an exercise for you to en devour upon. Additionally, you also need to check boundary conditions associated to tailleMax.

#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#define tailleMax 100


typedef struct elementList
{
    int valeurElem;
    int indexSuivant;
    int indexElem;

} elementList;


typedef struct list{

    elementList tabList[tailleMax];
    int debut;
    int fin;

} listT;


// To initialize the list 
void initListT(listT *list)
{
    for(int i = 0; i < tailleMax; i++)
    {
        list->tabList[i].valeurElem      = -1;
        list->tabList[i].indexSuivant    = -1;
        list->tabList[i].indexElem       = -1;

    }

}


// To create a new linked list
listT *creerListeT()
{
    listT *alist = (listT *)malloc(sizeof(listT));

    initListT(alist);
    alist->debut = 0;
    alist->fin   = 0;

    return alist;
}


// To test if the list is empty
bool estVideListT(listT *list)
{
    return list->tabList[ 0 ].valeurElem   ==  -1 ; 
}


// Function To inser in the head of the linked list 
listT *insererTeteListT(listT *list, int elemInserer)
{
    if( estVideListT(list) )
    {
        int a = list->debut;
        list->tabList[ a ].valeurElem     = elemInserer;
        list->tabList[ a ].indexSuivant   = list->debut + 1;
        list->tabList[ a ].indexElem      = list->debut;

        return list;
    }
    else // Cas de liste non vide
    {
        int i = 0;

        // On cherche l'indice de la première case vide
        while(list->tabList[i].valeurElem != -1)
        {
            i++;
        }

        // Un élément est dans la tête de la liste s'il n'y aucun élément qui le pointe
        list->tabList[ i ].valeurElem   = elemInserer;
        list->tabList[ i ].indexSuivant = list->debut;
        list->debut = i;

        return list;
    }

}


// Function to print the elements of  the list 
void printList(listT *list)
{
    if( estVideListT(list) )  // testing if the array is empty
    {
        printf("The array is empty\n");
    }
    else
    {
        // To revise
        int i = 0;

        while( list->tabList[i].indexSuivant != -1 )
        {
            printf("Element with index %d is : %d \n", i, list->tabList[i].valeurElem);
            i++;
        }

        printf("Element with index %d (Last element) is : %d \n", i-1, list->tabList[i-1].valeurElem);

    }
}

int main()
{
    // Creating the list
    listT *myList =  creerListeT();

    // Insertion of the elements in the list 
    insererTeteListT(myList, 5);
    insererTeteListT(myList, 3);
    insererTeteListT(myList, 2);
    insererTeteListT(myList, 4);
    insererTeteListT(myList, 7);

    // Printing the list 
    printList(myList);

    return 0;
}

Answer 2

In the following code:

// To initialize the list 
void initListT(listT list)
{
    for(int i = 0; i < tailleMax; i++)
    {
        list.tabList[i].valeurElem      = -1;
        list.tabList[i].indexSuivant    = -1;
        list.tabList[i].indexElem       = -1;

    }

}

Since you are passing list by value, all of your changes are local to the list variable in this function.