队列&栈//克隆图

克隆一张无向图，图中的每个节点包含一个 label （标签）和一个 neighbors （邻接点）列表 。

OJ的无向图序列化：

节点被唯一标记。

我们用 # 作为每个节点的分隔符，用 , 作为节点标签和邻接点的分隔符。

例如，序列化无向图 {0,1,2#1,2#2,2}。

该图总共有三个节点, 被两个分隔符  # 分为三部分。 

1. 第一个节点的标签为 0，存在从节点 0 到节点 1 和节点 2 的两条边。
2. 第二个节点的标签为 1，存在从节点 1 到节点 2 的一条边。
3. 第三个节点的标签为 2，存在从节点 2 到节点 2 (本身) 的一条边，从而形成自环。

我们将图形可视化如下：

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

/**
 * 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;
        HashMap<UndirectedGraphNode,UndirectedGraphNode> hashMap = new HashMap<>();
        LinkedList<UndirectedGraphNode> queue = new LinkedList<>();
        UndirectedGraphNode head = new UndirectedGraphNode(node.label);
        hashMap.put(node,head);
        queue.offer(node);
        while(!queue.isEmpty()){
            UndirectedGraphNode curNode = queue.poll();
            for(UndirectedGraphNode neighbor:curNode.neighbors){
                if(hashMap.containsKey(neighbor)==false){
                    queue.offer(neighbor);
                    UndirectedGraphNode newNeighbor = new UndirectedGraphNode(neighbor.label);
                    hashMap.put(neighbor,newNeighbor);
                }
                hashMap.get(curNode).neighbors.add(hashMap.get(neighbor));
            }
        }
        return head;
    }
}

public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {//DFS
        if (node == null) return null;
        HashMap<UndirectedGraphNode, UndirectedGraphNode> hashMap = new HashMap<>();
        UndirectedGraphNode head = new UndirectedGraphNode(node.label);
        hashMap.put(node, head);
        DFSSearch(hashMap, node);
        return head;
    }

    private void DFSSearch(HashMap<UndirectedGraphNode, UndirectedGraphNode> hashMap, UndirectedGraphNode node) {
        if (node == null) return;
        for (UndirectedGraphNode neighbor : node.neighbors) {
            if (hashMap.containsKey(neighbor) == false) {
                UndirectedGraphNode newNeighbor = new UndirectedGraphNode(neighbor.label);
                hashMap.put(neighbor, newNeighbor);
                DFSSearch(hashMap, neighbor);
            }
            hashMap.get(node).neighbors.add(hashMap.get(neighbor));
        }
    }。

/**
 * Definition for undirected graph.
 * struct UndirectedGraphNode {
 *     int label;
 *     vector<UndirectedGraphNode *> neighbors;
 *     UndirectedGraphNode(int x) : label(x) {};
 * };
 */
class Solution {
public:
    map<int,UndirectedGraphNode*> A;
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
        if(!node) return NULL;
        UndirectedGraphNode *p = new UndirectedGraphNode(node->label);
        A[node->label] = p;
        for(auto &x:node->neighbors)
            if(!A.count(x->label)) p->neighbors.push_back(cloneGraph(x));
            else p->neighbors.push_back(A[x->label]);
        return p;
    }
};