力扣：236. 二叉树的最近公共祖先

class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if(root==null||root==p||root==q) return root;
        TreeNode Lnode = lowestCommonAncestor(root.left, p, q);
        TreeNode Rnode = lowestCommonAncestor(root.right, p, q);
        if(Lnode==null&&Rnode==null) return null;
        if(Lnode==null) return Rnode;
        if(Rnode==null) return Lnode;
        return root;
    }
}