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) {                UndirectedGraphNode *retNode = NULL;        map<UndirectedGraphNode*, UndirectedGraphNode*> nodeMap;        list<UndirectedGraphNode *> nodeList;                if (node == NULL)            return NULL;                nodeList.push_back(node);                retNode = new UndirectedGraphNode(node->label);        nodeMap[node] = retNode;                while (nodeList.size() > 0)        {            UndirectedGraphNode *curNode = nodeList.front();            UndirectedGraphNode *clonedNode = nodeMap[curNode];            nodeList.pop_front();                    for (int i=0; i<curNode->neighbors.size(); i++)            {                UndirectedGraphNode *oldNeighborNode = curNode->neighbors[i];                                if (nodeMap.find(oldNeighborNode) == nodeMap.end())                {                    UndirectedGraphNode *newNeighborNode = new UndirectedGraphNode(oldNeighborNode->label);                    nodeList.push_back(oldNeighborNode);                    nodeMap[oldNeighborNode] = newNeighborNode;                }                                clonedNode->neighbors.push_back(nodeMap[oldNeighborNode]);            }        }        return retNode;    }};