Anon Ymous Anon Ymous - 1 year ago 169
Java Question

Java - Including BST

I have this BST problem I'm trying to solve in java, but I don't know why it's not working.
Here's the problem:

  • Binary search tree (BST) is a binary tree where the value of each
    node is larger or equal to the values in all the nodes in that node's
    left subtree and is smaller than the values in all the nodes in that
    node's right subtree.

    Write a function that checks if a given binary search tree contains a
    given value.

    For example, for the following tree:

    n1 (Value: 1, Left: null, Right: null) n2 (Value: 2, Left: n1, Right:
    n3) n3 (Value: 3, Left: null, Right: null) Call to contains(n2, 3)
    should return true since a tree with root at n2 contains number 3.

This is how I am trying to solve it:

class Node {
public int value;
public Node left, right;

public Node(int value, Node left, Node right) {
this.value = value;
this.left = left;
this.right = right;

public class BinarySearchTree {
public static boolean contains(Node root, int value) {
if(root.value == value)
return true;

else if(value < root.value){
if(root.left == null)
return false;
contains(root.left, value);
else if(value > root.value){
if(root.right == null)
return false;
contains(root.right, value);

return false;

public static void main(String[] args) {
Node n1 = new Node(1, null, null);
Node n3 = new Node(3, null, null);
Node n2 = new Node(2, n1, n3);

System.out.println(contains(n2, 3));

This should return true, but it doesn't... Thank you in advance.

Answer Source

return contains(...) instead of just calling contains(...) for those recursive calls, so that you don't lose values when they are made

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