二进制搜索树插入（C）

Question

Thanks, now for some reason it's not working as intended. When I run the program it just gives an error "bst.exe has stopped working" and it happens in this function.

static NODE *insert_i(NODE *r, int x)
{
    NODE *leaf;

    while(r)
    {
        if(r->val == x)
            return r;

        if(x < r->val && r->left != NULL)
            r = r->left;

        else if(x > r->val && r->right != NULL)
            r = r->right;
    }

    leaf = malloc(sizeof(NODE));
    leaf->left = NULL;
    leaf->right = NULL;
    leaf->val = x;
    count++;

    if(x < r->val)
        r->left = leaf;

    else
        r->right = leaf;

    return r;
}


void bst_insert(BST_PTR t, int x)
{
    t->root = insert_i(t->root, x);
}

Answer 1

You have

while(r)
{
    if(r == NULL)

The if condition will never be true, as if r is NULL then the loop will end, without returning anything from the function.

Answer 2

What will happen if you while loop is not entered or exited without returning? It will not return anything and behaviour will be undefined.

So, return NULL to indicate that not found or move if(r==NULL) out of the loop. It will not be executed inside the loop.