LowestCommonAncestorBST.java

import java.util.*;
import java.io.*;

class Node {
    Node left;
    Node right;
    int data;
    
    Node(int data) {
        this.data = data;
        left = null;
        right = null;
    }
}

class Solution {

  // As this is a BST we must find the node where v1 goes to one branch and v2 to the another one
	public static Node lca(Node root, int v1, int v2) {
        int data = root.data;
        Node left = root.left;
        Node right = root.right;

      	if (left != null && v1 < data && v2 < data) {
            return lca(left, v1, v2);
        }

        if (right != null && v1 > data && v2 > data) {
            return lca(right, v1, v2);
        }

        return root;
    }

	public static Node insert(Node root, int data) {
        if(root == null) {
            return new Node(data);
        } else {
            Node cur;
            if(data <= root.data) {
                cur = insert(root.left, data);
                root.left = cur;
            } else {
                cur = insert(root.right, data);
                root.right = cur;
            }
            return root;
        }
    }

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int t = scan.nextInt();
        Node root = null;
        while(t-- > 0) {
            int data = scan.nextInt();
            root = insert(root, data);
        }
      	int v1 = scan.nextInt();
      	int v2 = scan.nextInt();
        scan.close();
        Node ans = lca(root,v1,v2);
        System.out.println(ans.data);
    }	
}