在二叉树中找到两个节点的最近公共祖先

import java.util.*;



public class Solution {
    
    public int lowestCommonAncestor (TreeNode root, int o1, int o2) {
        // write code here
        if(root == null){
            return -1;
        }
        
        if(o1 == root.val || o2 == root.val){
            return root.val;
        }
        
        int left = lowestCommonAncestor(root.left, o1, o2);
        int right = lowestCommonAncestor(root.right, o1, o2);
        
        if(left == -1){
            return right;
        }
        
        if(right == -1){
            return left;
        }
        
        return root.val;
    }
}