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:

1. The number of nodes will be between 1 and 100.
2. The undirected graph is a simple graph, which means no repeated edges and no self-loops in the graph.
3. Since the graph is undirected, if node p has node q as neighbor, then node q must have node p as neighbor too.
4. 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;
     }
 };