LeetCode: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 from 0 to N - 1, where N is the total nodes in the graph.

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

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

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

1. Connect node 0 to both nodes 1 and 2.
2. Connect node 1 to node 2.
3. Connect node 2 to node 2 (itself), thus forming a self-cycle.

Visually, the graph looks like the following:

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

广度优先搜索。题目我调试了一大会，程序老有问题。

/**
 * Definition for undirected graph.
 * class UndirectedGraphNode {
 *     int label;
 *     ArrayList<UndirectedGraphNode> neighbors;
 *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 * };
 */
public class Solution {
    Map<Integer, UndirectedGraphNode> nodeMap = new HashMap<Integer, UndirectedGraphNode>();
	public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
		if (node == null) {
			return null;
		}
        
		LinkedList<UndirectedGraphNode> stack = new LinkedList<UndirectedGraphNode>();
		//Map<Integer, UndirectedGraphNode> nodeMap = new HashMap<Integer, UndirectedGraphNode>();
		nodeMap.clear();
		Set<Integer> isFound = new HashSet<Integer>();
		
		stack.addLast(node);
		
		UndirectedGraphNode head = null;
		
		while (!stack.isEmpty()) {
			UndirectedGraphNode first = stack.getFirst();
			stack.removeFirst();
			
			int label = first.label;
			
			UndirectedGraphNode n = nodeMap.get(label);
			if (n == null) {
				n = new UndirectedGraphNode(label);
				nodeMap.put(label, n);
			}
			
			if (head == null) {
				head = n;
			}
			
			if (!isFound.contains(label)) {
				isFound.add(label);
				
				ArrayList<UndirectedGraphNode> neighbors = first.neighbors;
				
				for (UndirectedGraphNode nb : neighbors) {
					UndirectedGraphNode nn = nodeMap.get(nb.label);
					if (nn == null) {
						nn = new UndirectedGraphNode(nb.label);
						nodeMap.put(nb.label, nn);
						
						stack.addLast(nb);
					}
					n.neighbors.add(nn);				}
			}
			
			
		}
		
		return head;
    }

}