133.cpp

// Clone graph
// MEDIUM

#include <bits/stdc++.h>
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) {
        return node ? cloneHelper(node) : nullptr;
    }

private:
    map<Node*, Node*> mp;
    
    Node* cloneHelper(Node* node) {
        if (mp.find(node) == mp.end()) {
            mp[node] = new Node(node->val);
        } else {
            return mp[node];
        }

        for (auto ngb : node->neighbors) {
            mp[node]->neighbors.push_back(cloneHelper(ngb));
        }

        return mp[node];
    }
};