Search key in binary tree

Question

the problem that I have is that for certain keys my function works, but for some it doesn't. The function should return a pointer to the node with the key == givenKey or NULL if there is no element in tree with that key. This is the structure and below is the function.

typedef struct node
{
    int key;
    struct node *l, *r;
}NodeT;

NodeT *search(NodeT *root, int givenKey)
{
    if(root == NULL || root->key == givenKey)
        return root;
    search(root->l, givenKey);
    search(root->r, givenKey);
}

This is the call of the function in main:

    NodeT *q = search(root, 9);
    NodeT *r = search(root, 7);
    printf("%p\n%p\n", q, r);

And this is the given binary tree: (for example q gets the right address, but r will be NULL even though there is an element with key = 7 in our binary tree.

I would really appreciate if you tell me what is wrong, because I tried to change the function a lot of times, but it didn't work. I even looked through my code with the debugger, but it doesn't seem to help that much. Thank you in advance!

Enable compiler warnings. They would have told you what is wrong. — klutt, Aug 20 '20 at 13:51

score 1 · Accepted Answer · answered Aug 20 '20 at 13:58

Check root if it contains the key, and children recursively. It return NULL if no nodes with the key found.

NodeT* search(NodeT* root, int givenKey)
{
    if (!root)
        return NULL;
    else if (root->key == givenKey)
        return root;

    NodeT* search_child_result = NULL;
    if (root->l)
    {
        search_child_result = search(root->l, givenKey);
        if (search_child_result)
            return search_child_result;
    }

    if (root->r)
    {
        search_child_result = search(root->r, givenKey);
        if (search_child_result)
            return search_child_result;
    }

    return search_child_result;
}

Search key in binary tree

1 Answers1