133. Clone Graph
题目
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:
1
/ \
/ \
0 --- 2
/ \
\_/
解析
- 考察图的基本遍历方法，DFS/BFS
- 注意细节bug
- 运用
unordered_map<UndirectedGraphNode*, UndirectedGraphNode*> hash进行图的映射关系存储
// clone graph
class Solution_133 {
// date 2017/12/29 10:01
// date 2017/12/29 11:04
public:
UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
unordered_map<UndirectedGraphNode*, UndirectedGraphNode*> hash;
if (!node)
{
return node;
}
if (hash.find(node)!=hash.end()) //找到，关键字已经访问过
{
hash[node] = new UndirectedGraphNode(node->label);
for (auto iter: node->neighbors)
{
hash[node]->neighbors.push_back(cloneGraph(iter)); //递归DFS //超时
}
}
return hash[node];
}
UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) //BFS
{
if (!node)
{
return node;
}
unordered_map<UndirectedGraphNode*, UndirectedGraphNode*> hash;
UndirectedGraphNode* head = new UndirectedGraphNode(node->label);
hash[node] = head;
queue<UndirectedGraphNode*> que;
que.push(node); //que.push(head); bug 花费1小时查找
while (!que.empty())
{
UndirectedGraphNode* q = que.front();
que.pop();
for (auto iter: q->neighbors)
{
if (!hash[iter]) //还没有访问
{
UndirectedGraphNode* temp = new UndirectedGraphNode(iter->label);
hash[iter] = temp;
que.push(iter);
}
hash[q]->neighbors.push_back(hash[iter]); //将一个节点的邻接点关系记录下来
}
}
return hash[node];
}
};
题目来源
