Binary search tree (BST) inorder visit that prints "The BST is in order" - binary-search-tree

Question

I am currently working on a Binary Search Tree project, and I would like to implement an "inorder" visit function:
void inorder(struct node *root)
{
if(root!=NULL) // checking if the root is not null
{
inorder(root->left_child); // visiting left child
printf(" %d ", root->data); // printing data at root
inorder(root->right_child);// visiting right child
}
}
However I do have a little issue, my BST varies between 100000 and 1000000 keys, and as you can imagine, printing them all is not very "handy". Is there perhaps a way to modify this inorder function in a way that it only prints "The BST is in order"? I have been trying to implement it but I really can't find a solution.
Thanks in advance for your help! Wish you a lovely coding session!

Answer 1

It looks like you want to verify whether a tree is actually a valid BST, i.e. its in-order traversal would visit its values in non-decreasing order.
For that you need a different function. Here is how it could be done:
int isValidBstHelper(struct node *root, int low, int high) {
return root == NULL ||
(root->data >= low && root->data <= high &&
isValidBstHelper(root->left_child, low, root->data) &&
isValidBstHelper(root->right_child, root->data, high));
}
int isValidBst(struct node *root) {
return isValidBstHelper(root, INT_MIN, INT_MAX);
}
isValidBst will return 1 when the tree is a valid BST and 0 when it is not.
To print the result, just call like this:
if (isValidBst(root)) {
printf("The tree is a valid BST");
} else {
printf("The tree is NOT a valid BST");
}