Just do Inorder traversal and make sure that the numbers are printed in increasing order assuming that the key is integer! Looking back, inorder traversal prints BST in ascending order.
1
Anonym
5. Juli 2011
The left subtree of a node contains only nodes with keys less than the node's key.
The right subtree of a node contains only nodes with keys greater than the node's key.
Both the left and right subtrees must also be binary search trees.