[LeetCode] 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 #.

1. First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node is labeled as 1. Connect node 1 to node 2.
3. 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
         / \
         \_/

/**
 * 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 == NULL) return NULL;
        unordered_map<UndirectedGraphNode *,UndirectedGraphNode *> nodeMap;
        queue<UndirectedGraphNode *> visit;
        visit.push(node);
        UndirectedGraphNode * copyNode = new UndirectedGraphNode(node -> label);
        nodeMap[node] = copyNode;
        while(visit.size() > 0){
            UndirectedGraphNode *cur = visit.front();
            visit.pop();
            for(int i = 0;i < cur -> neighbors.size();i ++){
                UndirectedGraphNode *neighbor = cur -> neighbors[i];
                if(nodeMap.find(neighbor) == nodeMap.end()){
                    UndirectedGraphNode *neighborCopy = new UndirectedGraphNode(neighbor -> label);
                    nodeMap[cur] -> neighbors.push_back(neighborCopy);
                    nodeMap[neighbor] = neighborCopy;
                    visit.push(neighbor);
                }else{
                    nodeMap[cur] ->neighbors.push_back(nodeMap[neighbor]);
                }
            }
        }
        return copyNode;
    }
};