ctci-is-binary-search-tree

//https://www.hackerrank.com/challenges/ctci-is-binary-search-tree

/* Hidden stub code will pass a root argument to the function below. Complete the function to solve the challenge. Hint: you may want to write one or more helper functions.

The Node class is defined as follows:
    class Node {
        int data;
        Node left;
        Node right;
     }
*/
    boolean checkBST(Node root) {
        if(root.left != null){
            if(root.left.data < root.data){//ez a helyes
                if(!checkBST(root.left)){
                    return false;
                }
            }
            else{//nem felel meg
                return false;
            }
        }
        if(root.right != null){
            if(root.right.data > root.data){//ez a helyes
                if(!checkBST(root.right)){
                    return false;
                }
            }
            else{
                return false;
            }
        }
        return true;
    }