Method is_adjacent

code/chapter08/graph_adjlist.rs:155–157

判断两个点是否相邻

(&self, from: &T, to: &T)

    // 判断两个点是否相邻
    fn is_adjacent(&self, from: &T, to: &T) -> bool {
        self.vertices.get(from).unwrap().adjacent_key(to)
    }
}

fn main() {