TreeNode getLastCommonParent(TreeNode root,TreeNode t1,TreeNode t2){
        if(findNode(root.left,t1)){
            if(findNode(root.right,t2)){
                return root;
            }else{
                return getLastCommonParent(root.left,t1,t2);
            }
        }else{
            if(findNode(root.left,t2)){
                
 
return root;
            }else{
                return getLastCommonParent(root.right,t1,t2)
            }
        }
    }
    // 查找節點node是否在當前 二叉樹中
    boolean findNode(TreeNode root,TreeNode node){
        if(root == null || node == null){
            return false;
        }
        if(root == node){
            
 
return true;
        }
        boolean found = findNode(root.left,node);
        if(!found){
            found = findNode(root.right,node);
        }
        return found;
    }

求兩個二叉樹的最低公共祖先節點