#### Find the Middle Node of a Singly Linked List

To find the middle node of a singly linked list, simply traverse the list until you reach the middle. If the list has an even number of nodes, return the node at the end of the first half of the list.

#### Problem

```Given a singly linked list, return the middle node of the list. If the list has an even number of nodes, return the node at the end of the first half of the list.
Example input: 1 -> 2 -> 3 -> 4 -> 5
Example output: 3```

#### Solution

This solution is in Python. Our A.I. can create solutions in multiple languages.
```# The optimal solution is to use two pointers, one that moves one node at a time and another that moves two nodes at a time.
# When the second pointer reaches the end of the list, the first pointer will be at the middle of the list.
# This solution is optimal because it only requires one pass through the list.

class Node:
def __init__(self, data):
self.data = data
self.next = None

def __init__(self):

def append(self, data):
new_node = Node(data)
return
while last_node.next:
last_node = last_node.next
last_node.next = new_node

def print_list(self):
while cur_node:
print(cur_node.data)
cur_node = cur_node.next

def middle _node(self):
while fast_pointer and fast_pointer.next:
slow_pointer = slow_pointer.next
fast_pointer = fast_pointer.next.next
return slow_pointer.data

llist.append(1)
llist.append(2)
llist.append(3)
llist.append(4)
llist.append(5)
llist.append(6)

print(llist.middle_node())```

A.I. Evaluation of the Solution

The candidate's solution is correct and demonstrates a level of completeness. The approach is also optimal, as it only requires one pass through the list.

Evaluated at: 2022-11-20 06:16:11