LeetCode

LeetCode地址:https://leetcode.com/problems/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 #.

  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
     / 
     _/
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/**
* Definition for undirected graph.
* class UndirectedGraphNode {
* int label;
* List<UndirectedGraphNode> neighbors;
* UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
* };
*/

public class {
public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
if(node==null)
return null;

HashMap<Integer,UndirectedGraphNode> graphMap=new HashMap<Integer,UndirectedGraphNode>();
Queue<UndirectedGraphNode> visit=new LinkedList<UndirectedGraphNode>();
UndirectedGraphNode temp;

visit.add(node);

while(!visit.isEmpty())
{
temp=visit.poll();

if(!graphMap.containsKey(temp.label))
{
UndirectedGraphNode graphNode=new UndirectedGraphNode(temp.label);
graphMap.put(temp.label, graphNode);

visit.addAll(temp.neighbors);
}
}

visit.add(node);
while(!visit.isEmpty())
{
temp=visit.poll();
UndirectedGraphNode graphNode=graphMap.get(temp.label);
if(graphNode.neighbors.size()==0 && temp.neighbors.size()!=0)
{
for(UndirectedGraphNode neighbor:temp.neighbors)
{
graphNode.neighbors.add(graphMap.get(neighbor.label));
visit.add(neighbor);
}
}
}

return graphMap.get(node.label);
}
}