# [133\. Clone Graph](https://leetcode.com/problems/clone-graph/)

:::spoiler Hint

/*
// Definition for a Node.
class Node {
public:
    int val;  // Value of the node
    vector<Node*> neighbors;  // List of neighbors (adjacent nodes)

    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 {
private:
    // Map to store the mapping between original nodes and their clones
public:
    Node* cloneGraph(Node* node)
    {
        // If the input node is null, return null

        // If the node has already been cloned, return its clone

        // Create a new clone for the current node

        // Recursively clone all the neighbors of the current node
        for ()
        {
            // Add the cloned neighbor to the current node's clone's neighbor list
        }
        // Return the clone of the current node
    }
};

:::

:::spoiler Solution

/*
// 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 {
private:
    unordered_map<Node*, Node*> m;
public:
    Node* cloneGraph(Node* node)
    {
        if (!node) return nullptr;
        if (m.count(node)) return m[node];

        m[node] = new Node(node->val);

        for (auto& nei : node->neighbors)
        {
            m[node]->neighbors.push_back(cloneGraph(nei));
        }
        return m[node];
    }
};

- T: $O(V + E)$
- S: $O(V)$
:::