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REDBEAN
REDBEAN

Reputation: 21

Linked list function works when called normally, but doesnt work when called in an IF statement?

So firstly I have IntListInsert which simply populates the list

void IntListInsert(IntList L, int v)
{
    assert(L != NULL);
    struct IntListNode *n = newIntListNode(v);
    if (L->first == NULL)
        L->first = L->last = n;
    else {
        L->last->next = n;
        L->last = n;
    }
    L->size++;
}

Then I have another sorting function If I simply call IntListInsert like this, it populates the lists properly, although not sorted.

void IntListInsertInOrder(IntList L, int v)
{
    
        IntListInsert(L, v);
}
$./list 1 2 3
123

When I try an IF statement to handle empty lists, It only inserts the first object in the list...

void IntListInsertInOrder(IntList L, int v)
{
    //check if list is empty
    if (L->first == NULL) {
        IntListInsert(L, v);
    }
}

$./list 1 2 3
1

Greatly appreciate any input :)

Upvotes: 0

Views: 73

Answers (3)

Vlad from Moscow
Vlad from Moscow

Reputation: 311048

The function IntListInsert appends only one node in each its call.

When the passed list is empty the function sets the pointer first of the list to the newly created node.

if (L->first == NULL)
        L->first = L->last = n;

So after exiting the function L->first is not equal to NULL.

On the other hand the function IntListInsertInOrder calls the function IntListInsert only when the list is initially empty.

void IntListInsertInOrder(IntList L, int v)
{
    //check if list is empty
    if (L->first == NULL) {
        IntListInsert(L, v);
    }
}

So what you are doing is what you are getting.

Upvotes: 0

DanielRadl
DanielRadl

Reputation: 101

How do you call the IntListInsertInOrder function? I think the problem is if (L->first == NULL) is only true for the first input 1. After u assigned 1 to the list if (L->first == NULL) is false.

Upvotes: 1

Julien
Julien

Reputation: 528

After you've inserted your first value, L->first is no more NULL and the if prevents from inserting other values ? The full code would be usefull

Upvotes: 0

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