def merge(left, right):
"""
Merges two linked lists sorting by data in nodes
Returns a new, merge list
Takes O(n) time
"""
# Create a new linked list that contains nodes from
# merging left and right
merged = LinkedList()
# Add a fake head that is discarded later
merged.add(0)
# Set current to the head of the linked list
current = merged.head
# Obtain head nodes for left and right linked list
right_head = right.head
left_head = left.head
# Iterate over left and right until we reach the tail node of either
while left_head or right_head:
# If the head node of left is None, we're past the tail
# Add the node from right to merged linked list
if left_head is None:
current.next_node = right_head
# Call next on right to set loop condition to false
right_head = right_head.next_node
# If the head node of right is None, We're past the tail
# Add the tail node from left to merged linked list
elif right_head is None:
current.next_node = left_head
# Call next on left to set loop condition to false
left_head = left_head.next_node
else:
# Not at either tail node
# Obtain node data to perform comparison operations
left_data = left_head.data
right_data = right_head.data
# If data on left is less than right, set current to left node
if left_data < right_data:
current.next_node = left_head
# Move left head to next node
left_head = left_head.next_node
# If data on left is greater than right, set current to right node
else:
current.next_node = right_head
# Move right head to next node
right_head = right_head.next_node
# Move current to next node
current = current.next_node
# Discard fake head and set first merge node as head
head = merged.head.next_node
merged.head = head
return merged
right_data = right_head.data
# If data on left is less than right, set current to left node
if left_data < right_data:
current.next_node = left_head
# Move left head to next node
left_head = left_head.next_node
# If data on left is greater than right, set current to right node
else:
current.next_node = right_head
# Move right head to next node
right_head = right_head.next_node
# Move current to next node
current = current.next_node
# Discard fake head and set first merge node as head
head = merged.head.next_node
merged.head = head
return merged
l = LinkedList()
l.add(12)
l.add(4)
l.add(45)
l.add(5)
l.add(34)
print(l)
sorted_list = merge_sort(l)
print(sorted_list)
