0138Copy List_with_Random_Pointer.cpp

/*
// Definition for a Node.
class Node {
public:
    int val;
    Node* next;
    Node* random;
    
    Node(int _val) {
        val = _val;
        next = NULL;
        random = NULL;
    }
};
*/

class Solution {
public:
    Node* copyRandomList(Node* head) {
        if (!head) return nullptr;
        
        std::unordered_map<Node*, Node*> nodeMap;
        
        Node* current = head;
        while (current) {
            nodeMap[current] = new Node(current->val);
            current = current->next;
        }
        
        
        current = head;
        while (current) {
            nodeMap[current]->next = nodeMap[current->next];
            nodeMap[current]->random = nodeMap[current->random];
            current = current->next;
        }
        
        return nodeMap[head];
    }
};