LeetCode OJ:Clone Graph

Clone Grap

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
         / \
         \_/

题目意思很简单，就是给一个可以有回路的图，从任意给的节点开始，将这个图复制一遍，返回任给的这个节点的复制节点。

算法思想：

我们可以采用广度优先搜索的方法来遍历这张图，根据每个节点进行复制，所以用到了队列这个数据结构，遍历各节点时，将该节点指针push到队列中；

因为同时考虑到两种情况：1、回路如何判重；2、怎样实现已知节点与根据该节点复制的节点的一一对应，所以我用到了map这个数据结构，实现

已知节点指针到复制节点指针的映射。

class Solution{
public:
	UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node){
		if(!node)return NULL;
		UndirectedGraphNode *head=new UndirectedGraphNode(node->label);	
		queue<UndirectedGraphNode *> store;
		map<UndirectedGraphNode *,UndirectedGraphNode *> mp;
		map<UndirectedGraphNode *,UndirectedGraphNode *>::iterator it;

		store.push(node);
		mp.insert(pair<UndirectedGraphNode *,UndirectedGraphNode *>(node,head));

		while(!store.empty()){
			UndirectedGraphNode *cur=store.front();
			UndirectedGraphNode *newNode=mp.find(cur)->second;//根据cur节点到该复制节点
			store.pop();
			for(int i=0;i<cur->neighbors.size();i++){
				it=mp.find(cur->neighbors[i]);
				if(it!=mp.end()){//如果该节点已经存在，说明有回路
					newNode->neighbors.push_back(it->second);
					continue;
				}
				UndirectedGraphNode *next=cur->neighbors[i];
				UndirectedGraphNode *t=new UndirectedGraphNode(next->label);
				newNode->neighbors.push_back(t);
				store.push(next);
				mp.insert(pair<UndirectedGraphNode *,UndirectedGraphNode *>(next,t));
			}
		}
		return head;
	}
};