Tree.java

package dsa.tree;

public class Tree {
 Node root;

 public static void main(String args[]) {
  Tree anyTree = new Tree();
  anyTree.root = new Node(3);
  anyTree.root.left = new Node(2);
  anyTree.root.right = new Node(5);
  anyTree.root.left.left = new Node(1);
  anyTree.root.left.right = new Node(4);
  
  
  if(anyTree.isBst(anyTree.root)){
   System.out.println("Is BST");
  }else{
   System.out.println("Is Not bst");
  }
 }

 private int MINVALUE = -1;
 
 public boolean isBst(Node node) {
  if(node.left!=null){
   if(!isBst(node.left)) return false;
  }
  if(node.data > MINVALUE){
   MINVALUE = node.data;
  }else{
   return false;
  }
  if(node.right!=null){
   if(!isBst(node.right)) return false;
  }
  return true;
 }
 
}