/**
 * Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.
 *
 * According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself).”
 *
 * Given binary search tree:  root = [6,2,8,0,4,7,9,null,null,3,5]
 *
 * Example 1:
 *
 * Input: root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 8
 * Output: 6
 * Explanation: The LCA of nodes 2 and 8 is 6.
 * Example 2:
 *
 * Input: root = [6,2,8,0,4,7,9,null,null,3,5], p = 2, q = 4
 * Output: 2
 * Explanation: The LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.
 *
 *
 * Note:
 *
 * All of the nodes' values will be unique.
 * p and q are different and both values will exist in the BST.
 */
public class BSTLowestCommonAncestor {
    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int x) { val = x; }
    }
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        int min = Math.min(p.val, q.val), max = Math.max(p.val, q.val);
        while (!(min <= root.val && root.val <= max)) {
            if (max < root.val) {
                root = root.left;
            } else {
                root = root.right;
            }
        }
        return root;
    }
}
