133. Clone Graph

Problem

Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.

OJ's undirected graph serialization:

Nodes are labeled uniquely.

We use # as a separator for each node, and , as a separator for node label and each neighbor of the node.

As an example, consider the serialized graph {0,1,2#1,2#2,2}.

The graph has a total of three nodes, and therefore contains three parts as separated by #.

• First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
• Second node is labeled as 1. Connect node 1 to node 2.
• Third node is labeled as 2. Connect node 2 to node 2 (itself), thus forming a self-cycle.

Visually, the graph looks like the following:

       1
      / \
     /   \
    0 --- 2
         / \
         \_/

Solution

/**
 * Definition for undirected graph.
 * function UndirectedGraphNode(label) {
 *     this.label = label;
 *     this.neighbors = [];   // Array of UndirectedGraphNode
 * }
 */

/**
 * @param {UndirectedGraphNode} graph
 * @return {UndirectedGraphNode}
 */
var cloneGraph = function(graph) {
  return clone(graph, {});
};

var clone = function (node, map) {
  if (!node) return null;
  if (map[node.label]) return map[node.label];

  var cloneNode = new UndirectedGraphNode(node.label);

  map[node.label] = cloneNode;

  for (var i = 0; i < node.neighbors.length; i++) {
    cloneNode.neighbors.push(clone(node.neighbors[i], map));
  }

  return cloneNode;
};

Explain:

不用管描述里的 # , 什么的，题意就是复制一个无向图，不要想复杂了。

注意有重复节点的话，存个引用就行，用哈希表判断是否重复。

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).