LeetCode133.克隆圖

可以使用DFS和BFS。參考https://blog.csdn.net/qq508618087/article/details/50806972

1.DFS 判斷當前節點是否被建立，如果建立直接返回。使用unordered_map來儲存已經建立的節點。遞迴訪問每個節點和每個鄰居

class Solution {
public:
	UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
		if (!node) return NULL;
		if (hash.count(node)) return hash[node];//當前unorder_map中已經存在直接反回
		hash[node] = new UndirectedGraphNode(node->label);
		for (auto val : node->neighbors)
			hash[node]->neighbors.push_back(cloneGraph(val));
		return hash[node];
	}

private:
	unordered_map<UndirectedGraphNode *, UndirectedGraphNode *>hash;
};
 

2.BFS 使用佇列來儲存已經構建好的節點。首先將起始節點放入佇列，然後進行廣度遍歷，遍歷的物件為當前節點的鄰居節點，如果還沒被建立，則建立並放入佇列。最後將會遍歷所有節點完成克隆。

class Solution {
public:
	UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
		if (!node) return NULL;
        UndirectedGraphNode* graph = new UndirectedGraphNode(node->label);
        hash[node] = graph;
        queue<UndirectedGraphNode*> q;
        q.push(node);
        while (!q.empty()) {
            auto curNode = q.front();
            q.pop();
            for (auto val : curNode->neighbors) {
                if (hash.find(val) == hash.end()) {
                    hash[val] = new UndirectedGraphNode(val->label);
                    q.push(val);
                }
                hash[curNode]->neighbors.push_back(hash[val]);
            }
        }
        return graph;
	}

private:
	unordered_map<UndirectedGraphNode *, UndirectedGraphNode *>hash;
};