Today I have done leetcode's December LeetCoding Challenge with cpp.

December LeetCoding Challenge 28

Description

Middle of the Linked List

Given the head of a singly linked list, return the middle node of the linked list.

If there are two middle nodes, return the second middle node.

Example 1:

Input: head = [1,2,3,4,5]
Output: [3,4,5]
Explanation: The middle node of the list is node 3.

Example 2:

Input: head = [1,2,3,4,5,6]
Output: [4,5,6]
Explanation: Since the list has two middle nodes with values 3 and 4, we return the second one.

Constraints:

• The number of nodes in the list is in the range [1, 100].
• 1 <= Node.val <= 100

Solution

class Solution {
  int length(ListNode *head) {
    int result = 0;
    while(head) {
      result += 1;
      head = head->next;
    }
    return result;
  }
  ListNode *advance(ListNode *head, int count) {
    while(count--) {
      head = head->next;
    }
    return head;
  }
public:
  ListNode* middleNode(ListNode* head) {
    return advance(head, length(head) / 2);
  }
};

// Accepted
// 36/36 cases passed (4 ms)
// Your runtime beats 40.59 % of cpp submissions
// Your memory usage beats 96.09 % of cpp submissions (7 MB)