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;
        
    }
}