带你读《图解算法小抄》七、图（2）

export default class GraphEdge {
  /**
   * @param {GraphVertex} startVertex
   * @param {GraphVertex} endVertex
   * @param {number} [weight=1]
   */
  constructor(startVertex, endVertex, weight = 0) {
    this.startVertex = startVertex;
    this.endVertex = endVertex;
    this.weight = weight;
  }
  /**
   * @return {string}
   */
  getKey() {
    const startVertexKey = this.startVertex.getKey();
    const endVertexKey = this.endVertex.getKey();
    return `{startVertexKey}_{startVertexKey}_{startVertexKey}_{endVertexKey}`;
  }
  /**
   * @return {GraphEdge}
   */
  reverse() {
    const tmp = this.startVertex;
    this.startVertex = this.endVertex;
    this.endVertex = tmp;
    return this;
  }
  /**
   * @return {string}
   */
  toString() {
    return this.getKey();
  }}

export default class LinkedListNode {
  constructor(value, next = null) {
    this.value = value;
    this.next = next;
  }
  toString(callback) {
    return callback ? callback(this.value) : `${this.value}`;
  }}