【leetcode-236】二叉树的最近公共祖先

/**
 * 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 || root.val == p.val || root.val == q.val) return root;
        TreeNode right = lowestCommonAncestor(root.right, p, q);
        TreeNode left = lowestCommonAncestor(root.left, p, q);
        if (left == null) return right;
        if (right == null) return left;
        return root;
    }
}