leetcode235_BST的最近公共祖先

利用BST有序的特点即可。

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