Middle of the Linked List LeetCode solution in C++

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/**
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 * Definition for singly-linked list.
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 * struct ListNode {
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 * int val;
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 * ListNode *next;
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 * ListNode() : val(0), next(nullptr) {}
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 * ListNode(int x) : val(x), next(nullptr) {}
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 * ListNode(int x, ListNode *next) : val(x), next(next) {}
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 * };
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 */
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class Solution {
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 public:
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  ListNode *middleNode(ListNode *head) {
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    ListNode *slow = head;
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    ListNode *fast = head;
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    while (fast != NULL && fast->next != NULL) {
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      slow = slow->next;
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      fast = fast->next->next;
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    }
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    return slow;
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  }
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};