20. Clone Graph.cpp

/*
Clone Graph
===========

Given a reference of a node in a connected undirected graph.

Return a deep copy (clone) of the graph.

Each node in the graph contains a val (int) and a list (List[Node]) of its neighbors.

class Node {
  public int val;
  public List<Node> neighbors;
}
 

Test case format:

For simplicity sake, each node's value is the same as the node's index (1-indexed). For example, the first node with val = 1, the second node with val = 2, and so on. The graph is represented in the test case using an adjacency list.

Adjacency list is a collection of unordered lists used to represent a finite graph. Each list describes the set of neighbors of a node in the graph.

The given node will always be the first node with val = 1. You must return the copy of the given node as a reference to the cloned graph.

 

Example 1:
Input: adjList = [[2,4],[1,3],[2,4],[1,3]]
Output: [[2,4],[1,3],[2,4],[1,3]]
Explanation: There are 4 nodes in the graph.
1st node (val = 1)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
2nd node (val = 2)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).
3rd node (val = 3)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
4th node (val = 4)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).


Example 2:
Input: adjList = [[]]
Output: [[]]
Explanation: Note that the input contains one empty list. The graph consists of only one node with val = 1 and it does not have any neighbors.


Example 3:
Input: adjList = []
Output: []
Explanation: This an empty graph, it does not have any nodes.


Example 4:
Input: adjList = [[2],[1]]
Output: [[2],[1]]


Constraints:
1 <= Node.val <= 100
Node.val is unique for each node.
Number of Nodes will not exceed 100.
There is no repeated edges and no self-loops in the graph.
The Graph is connected and all nodes can be visited starting from the given node.

*/

/*
// Definition for a Node.
class Node {
public:
    int val;
    vector<Node*> neighbors;
    
    Node() {
        val = 0;
        neighbors = vector<Node*>();
    }
    
    Node(int _val) {
        val = _val;
        neighbors = vector<Node*>();
    }
    
    Node(int _val, vector<Node*> _neighbors) {
        val = _val;
        neighbors = _neighbors;
    }
};
*/

class Solution
{
public:
  Node *cloneGraph(Node *src)
  {
    if (!src)
      return NULL;
    map<Node *, Node *> m;
    queue<Node *> q;

    q.push(src);
    Node *node;

    node = new Node();
    node->val = src->val;

    m[src] = node;
    while (!q.empty())
    {
      Node *u = q.front();
      q.pop();
      vector<Node *> v = u->neighbors;
      int n = v.size();
      for (int i = 0; i < n; i++)
      {
        if (m[v[i]] == NULL)
        {
          node = new Node();
          node->val = v[i]->val;
          m[v[i]] = node;
          q.push(v[i]);
        }

        m[u]->neighbors.push_back(m[v[i]]);
      }
    }
    return m[src];
  }
};