leetcode Clone Graph

Clone Graph

  Total Accepted: 2649  Total Submissions: 14045 My Submissions

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
         / \
         \_/

DFS is OK, TAKE NOTICE the position of

      exist.insert(make_pair(node, nodecpy));

The following is the AC code:

/**
 * Definition for undirected graph.
 * struct UndirectedGraphNode {
 *     int label;
 *     vector<UndirectedGraphNode *> neighbors;
 *     UndirectedGraphNode(int x) : label(x) {};
 * };
 */
class Solution {
 public:
  UndirectedGraphNode *DFS(UndirectedGraphNode *node, unordered_map<UndirectedGraphNode*, UndirectedGraphNode*>& exist) {
    if (exist.find(node) != exist.end())
      return exist[node];
    else {
      UndirectedGraphNode *nodecpy = new UndirectedGraphNode(node->label);
      exist.insert(make_pair(node, nodecpy));
      UndirectedGraphNode *neighbor = NULL;
      for (int i = 0; i < (node->neighbors).size(); ++i) {
        neighbor = DFS((node->neighbors)[i], exist);
        (nodecpy->neighbors).push_back(neighbor);
      }
      return nodecpy;
    }
      
  }
  UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
    unordered_map<UndirectedGraphNode*, UndirectedGraphNode*> exist;
    if (node == NULL)
      return node;
    return DFS(node,exist);
  }
};