leetcode之Clone Graph

最新推荐文章于 2025-08-11 17:34:21 发布

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本文详细介绍了无向图的克隆算法实现，包括使用BFS搜索和复制图的过程，以及如何通过数据结构实现这一过程。重点在于理解图的序列化与反序列化过程，以及如何利用哈希表来跟踪已访问的节点。

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题目大意:

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 #.

First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
Second node is labeled as 1. Connect node 1 to node 2.
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:

意思就是:

给定一个图, 复制图.

做题思路:

用BFS搜索, 并复制. 关键就是如何用已经给定的数据结构进行BFS. 我们需要两个数据结构: 1, stack/queue进行bfs的基本数据结构; 2, unordered_map 用来保存已经复制(遍历)的节点, 同时可以查看哪些节点已经被访问过了.

代码如下:

struct UndirectedGraphNode{
	int label;
	vector<UndirectedGraphNode*> neighbors;
	UndirectedGraphNode(int x) : label(x) {}
};
class Solution{
	public:
		UndirectedGraphNode* cloneGraph(UndirectedGraphNode* node){
			if(!node){
				return NULL;
			}
			UndirectedGraphNode* first = new UndirectedGraphNode(node->label);
			typedef unordered_map<int, UndirectedGraphNode*> MAP;
			MAP storage;
			storage.insert(make_pair(first->label, first));
			//stack<UndirectedGraphNode*> gstack;
			queue<UndirectedGraphNode*> gstack;
			gstack.push(node);
			while(!gstack.empty()){
				//UndirectedGraphNode *temp = gstack.top(), *newNode;
				UndirectedGraphNode *temp = gstack.front(), *newNode;
				if(storage.count(temp->label) == 0){
					newNode = new UndirectedGraphNode(temp->label);
					storage.insert(make_pair(temp->label, newNode));
				}
				else{
					newNode = storage[temp->label];
				}
				gstack.pop();
				for(int i=0;i<temp->neighbors.size();i++){
					if(storage.count(temp->neighbors[i]->label) == 0){
						storage.insert(make_pair(temp->neighbors[i]->label, new UndirectedGraphNode(temp->neighbors[i]->label)));
						gstack.push(temp->neighbors[i]);
					}
					newNode->neighbors.push_back(storage[temp->neighbors[i]->label]);
				}
			}
			return first;
		}
};