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) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        if (node == NULL) {
            return NULL;
        }
        unordered_map<int, UndirectedGraphNode *> visited;
        unordered_set<int> completed;
        queue<UndirectedGraphNode *> uncompleted;
        uncompleted.push(node);
        int start_node_label = node->label;
        
        while (!uncompleted.empty()) {
            UndirectedGraphNode *curr = uncompleted.front();
            uncompleted.pop();
            if(completed.find(curr->label) == completed.end()) {
                UndirectedGraphNode *copy;
                if (visited.find(curr->label) == visited.end()) {
                    copy = new UndirectedGraphNode(curr->label);
                    visited.insert(make_pair(copy->label, copy));
                } else {
                    copy = visited[curr->label];
                }
                for (UndirectedGraphNode *temp : curr->neighbors) {
                    if (visited.find(temp->label) != visited.end()) {
                        copy->neighbors.push_back(visited[temp->label]);
                    } else {
                        UndirectedGraphNode *neighbor = new UndirectedGraphNode(temp->label);
                        copy->neighbors.push_back(neighbor);
                        visited.insert(make_pair(neighbor->label, neighbor));
                    }
                }
                completed.insert(copy->label);
                for (UndirectedGraphNode *temp : curr->neighbors) {
                    if (completed.find(temp->label) == completed.end()) {
                    uncompleted.push(temp);
                    }
                }
            }
        }
        return visited[start_node_label];   
    }
};