/*
 * @lc app=leetcode id=235 lang=java
 *
 * [235] Lowest Common Ancestor of a Binary Search Tree
 */
/**
 * Definition for a binary tree node. public class TreeNode { int val; TreeNode
 * left; TreeNode right; TreeNode(int x) { val = x; } }
 */
class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if (root == null || p == null || q == null) {
            return null;
        }

        if (root.val > p.val && root.val > q.val) {
            return lowestCommonAncestor(root.left, p, q);
        }
        if (root.val < p.val && root.val < q.val) {
            return lowestCommonAncestor(root.right, p, q);
        }

        return root;
    }
}

class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        while (root != null) {
            if (root.val > p.val && root.val > q.val) {
                root = root.left;
            } else if (root.val < p.val && root.val < q.val) {
                root = root.right;
            } else {
                break;
            }
        }
        return root;
    }
}