message: Update copy-list-with-random-pointer.cpp
diff: // Time: O(n)
  // Space: O(1)
  -/**
  - * Definition for singly-linked list with a random pointer.
  - * struct RandomListNode {
  - * int label;
  - * RandomListNode *next, *random;
  - * RandomListNode(int x) : label(x), next(NULL), random(NULL) {}
  - * };
  +/*
  +// 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:
  - RandomListNode *copyRandomList(RandomListNode *head) {
  + Node* copyRandomList(Node* head) {
  // Insert the copied node after the original one.
  for (auto *curr = head; curr; curr = curr->next->next) {
  - auto *node = new RandomListNode(curr->label);
  + auto *node = new Node(curr->val);
  node->next = curr->next;
  curr->next = node;
  }
  @@ -27,7 +35,7 @@ public:
  }
  // Seperate the copied nodes from original ones.
  - RandomListNode dummy(0);
  + Node dummy(0);
  for (auto *curr = head, *copy_curr = &dummy;
  curr;
  copy_curr = copy_curr->next, curr = curr->next) {
  