Clone Graph.cpp

/*
// 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;
    }
};
*/
#include <vector>
#include <unordered_map>


using namespace std;

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* node)
    {
        unordered_map<Node*, Node*> m;
        return helper(node, m);
    }

    Node* helper(Node* node, unordered_map<Node*, Node*> &m)
    {
        if(node == nullptr) return nullptr;
        if(m.count(node)) return m[node];
        Node* clone = new Node(node->val);
        m[node] = clone;
        for(Node* neighbor: node->neighbors)
        {
            clone->neighbors.push_back(helper(neighbor, m));
        }
        return clone;
    }
};