Clone Graph

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 #.

1. First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node is labeled as 1. Connect node 1 to node 2.
3. 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

         / \

         \_/
很简单，BFS遍历，加上Map来保存label和节点地址

/**

 * Definition for undirected graph.

 * class UndirectedGraphNode {

 *     int label;

 *     List<UndirectedGraphNode> neighbors;

 *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }

 * };

 */

public class Solution {

    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {

        if(node == null)

            return null;

 

        LinkedList<UndirectedGraphNode> queue = new LinkedList<UndirectedGraphNode>();

        HashMap<UndirectedGraphNode, UndirectedGraphNode> map = 

                                   new HashMap<UndirectedGraphNode,UndirectedGraphNode>();

 

        UndirectedGraphNode newHead = new UndirectedGraphNode(node.label);

 

        queue.add(node);

        map.put(node, newHead);

 

        while(!queue.isEmpty()){

            UndirectedGraphNode curr = queue.pop();

            ArrayList<UndirectedGraphNode> currNeighbors = (ArrayList)curr.neighbors; 

 

            for(UndirectedGraphNode aNeighbor: currNeighbors){

                if(!map.containsKey(aNeighbor)){

                    UndirectedGraphNode copy = new UndirectedGraphNode(aNeighbor.label);

                    map.put(aNeighbor,copy);

                    map.get(curr).neighbors.add(copy);

                    queue.add(aNeighbor);

                }else{

                    map.get(curr).neighbors.add(map.get(aNeighbor));

                }

            }

 

        }

        return newHead;

        

    }

}