力扣算法——133.CloneGraph【M】

Given a reference of a node in a connected undirected graph, return a deep copy (clone) of the graph. Each node in the graph contains a val (int) and a list (List[Node]) of its neighbors.

Example:

Input:

{"$id":"1","neighbors":[{"$id":"2","neighbors":[{"$ref":"1"},{"$id":"3","neighbors":[{"$ref":"2"},{"$id":"4","neighbors":[{"$ref":"3"},{"$ref":"1"}],"val":4}],"val":3}],"val":2},{"$ref":"4"}],"val":1}

Explanation:

Node 1's value is 1, and it has two neighbors: Node 2 and 4.

Node 2's value is 2, and it has two neighbors: Node 1 and 3.

Node 3's value is 3, and it has two neighbors: Node 2 and 4.

Node 4's value is 4, and it has two neighbors: Node 1 and 3.

Note:

The number of nodes will be between 1 and 100.
The undirected graph is a simple graph, which means no repeated edges and no self-loops in the graph.
Since the graph is undirected, if node p has node q as neighbor, then node q must have node p as neighbor too.
You must return the copy of the given node as a reference to the cloned graph.

Soulution:

　　使用DFS和BFS即可

　　两种方法在leetcode中都能通过，但在牛客中，BFS使用的而外空间超出限制，所以只能使用DFS

 struct UndirectedGraphNode {

     int label;

     vector<UndirectedGraphNode *> neighbors;

     UndirectedGraphNode(int x) : label(x) {};

 };

 //DFS

 class Solution01 {

 public:

     UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {

         unordered_map<UndirectedGraphNode*, UndirectedGraphNode*>mapR;

         return helper(node, mapR);

     }

     UndirectedGraphNode* helper(UndirectedGraphNode*node, unordered_map<UndirectedGraphNode*, UndirectedGraphNode*>&mapR)

     {

         if (node == nullptr)return nullptr;

         if (mapR.find(node) != mapR.end())//旧节点

             return mapR[node];

         UndirectedGraphNode* res = new UndirectedGraphNode(node->label);//新节点

         mapR[node] = res;

         for (auto a : node->neighbors)

             res->neighbors.push_back(helper(a, mapR));

         return res;

     }

 };

 //BFS

 class Solution02 {

 public:

     UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {

         queue<UndirectedGraphNode*>qNode;

         qNode.push(node);

         unordered_map<UndirectedGraphNode*, UndirectedGraphNode*>mapR;

         UndirectedGraphNode *res = new UndirectedGraphNode(node->label);

         mapR[node] = res;

         while (!qNode.empty())

         {

             UndirectedGraphNode *p = qNode.front();

             qNode.pop();

             for (auto a : p->neighbors)

             {

                 if (mapR.find(a) == mapR.end())//新节点

                 {

                     qNode.push(a);//加入

                     mapR[a] = new UndirectedGraphNode(a->label);//新节点

                 }

                 mapR[p]->neighbors.push_back(mapR[a]);//连接节点

             }

         }

         return res;

     }

 };

巴特西

力扣算法——133.CloneGraph【M】

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