给无向连通图中节点的引用，返回图的深拷贝。

DFS

对访问过的节点进行标记，然后用dfs

• 时间复杂度O(n)，空间复杂度O(n)
• Runtime: 103 ms, faster than 23.59%
• Memory Usage: 39.7 MB, less than 95.77%

/**
 * // Definition for a Node.
 * function Node(val, neighbors) {
 *    this.val = val === undefined ? 0 : val;
 *    this.neighbors = neighbors === undefined ? [] : neighbors;
 * };
 */

/**
 * @param {Node} node
 * @return {Node}
 */
const visited = new Map();
var cloneGraph = function(node) {
  if (!node) {
    return node;
  }
  if (visited.has(node)) {
    return visited.get(node);
  }
  const cloneNode = new Node(node.val, []);
  visited.set(node,cloneNode);
  for (const i of node.neighbors) {
    cloneNode.neighbors.push(cloneGraph(i))
  }
  return cloneNode;
};

BFS

这个解法有点问题，会返回 You must return a copy of all the nodes in the original graph，应该是哪里没有深复制的原因

/**
 * // Definition for a Node.
 * function Node(val, neighbors) {
 *    this.val = val === undefined ? 0 : val;
 *    this.neighbors = neighbors === undefined ? [] : neighbors;
 * };
 */

/**
 * @param {Node} node
 * @return {Node}
 */
var cloneGraph = function(node) {
  const visited = new Map();
  const queue = [node];
  visited.set(node, new Node(node.val, []));
  while (queue.length > 0) {
    const n = queue.shift();
    for (const i of node.neighbors) {
      if(!visited.get(i)) {
        visited.set(i, new Node(i.val, []));
        queue.push(i);
      }
      visited.get(n).neighbors.push(visited.get(i));
    }
  }
  return visited.get(node);
};