133. Clone Graph

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
         / \
         \_/

S: DFS/BFS

记录已经克隆过的节点避免重复访问

/**
 * Definition for undirected graph.
 * struct UndirectedGraphNode {
 *     int label;
 *     vector<UndirectedGraphNode *> neighbors;
 *     UndirectedGraphNode(int x) : label(x) {};
 * };
 */
class Solution {
public:
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
        if (!node) {
            return NULL;
        }
        if (visited.find(node->label) != visited.end()) {
            return visited[node->label];
        }
        UndirectedGraphNode* cloneNode = new UndirectedGraphNode(node->label);
        visited[node->label] = cloneNode;
        for (const auto& i : node->neighbors) {
            cloneNode->neighbors.push_back(cloneGraph(i));
        }
        return cloneNode;
    }

private:
    unordered_map<int, UndirectedGraphNode*> visited;
};