Method print_node

publication/code/chapter09/dfs.rs:57–64

(&self)

    }

    fn print_node(&self) {
        let mut curr = self.first.clone();
        while let Some(val) = curr {
            print!("[{}]", &val.borrow().data);
            curr = val.borrow().next.clone();
        }
        print!("\n");
    }
}

// 构建图