C++

1class Solution {
2  public:
3    ListNode* middleNode(ListNode* head) {
4      int size = 0;
5
6      ListNode *temp = head;
7
8      while(temp)
9      {
10        ++size;
11        temp = temp->next;
12      }
13
14      size >>= 1;
15      temp = head;
16      for(int i=0;i<size; ++i)
17      {
18        temp = temp->next;
19      }
20
21      return temp;
22    }
23};

JavaScript

1var middleNode = function(head) {
2  let size = 0;
3
4  let temp = head;
5  while(temp) {
6    size+=1;
7    temp = temp.next;
8  }
9
10  size >>= 1;
11  temp = head;
12  for(let i=0; i<size; ++i) {
13    temp = temp.next;
14  }
15
16  return temp;
17};

Ruby

1def middle_node(head)
2  cnt = 0
3
4  temp = head
5  while temp
6    cnt += 1
7    temp = temp.next 
8  end
9
10  cnt >>= 1
11  temp = head
12  for i in (0...cnt) do
13    temp = temp.next 
14  end
15
16  temp
17end

Ruby pt.2

1def middle_node(head)
2  temp = head
3  cnt = 0
4  while temp
5    temp = temp.next
6    cnt += 1
7  end
8
9  temp = head
10  cnt = cnt / 2
11  for i in 0...cnt
12    temp = temp.next
13  end
14  temp
15end