Method add_edge

code/chapter08/graph_matrix.rs:54–60

添加边，设置边属性为 true

(&mut self, n1: &Vertex, n2: &Vertex)

    // 添加边，设置边属性为 true
    fn add_edge(&mut self, n1: &Vertex, n2: &Vertex) {
        if n1.id < self.nodes && n2.id < self.nodes {
           self.graph[n1.id][n2.id] = Edge::set_edge();
        } else {
            panic!("error");
        }
    }
}

fn main() {