def pivot(head, k):
less = ListNode(0)
equal = ListNode(0)
more = ListNode(0)
less_head, equal_head, more_head = less, equal, more
current = head
while current:
next_node = current.next_node
current.next_node = None
# Could do voodoo to make [equal, more, less] list, but this is clearer
if current.value == k:
equal.next_node = current
equal = equal.next_node
elif current.value > k:
more.next_node = current
more = more.next_node
else:
less.next_node = current
less = less.next_node
current = next_node
less.next_node = equal_head.next_node
equal.next_node = more_head.next_node
return less_head.next_node
def add(a, b):
result = ListNode(0)
result_head = result
carry = 0
while a or b or carry:
a_digit = a.value if a else 0
b_digit = b.value if b else 0
a = a.next_node if a else None
b = b.next_node if b else None
digit_sum = a_digit + b_digit + carry
new_digit = digit_sum % 10
carry = digit_sum / 10
result.next_node = ListNode(new_digit)
result = result.next_node
return result_head.next_node
result = next_node
head = next_node
else:
result.next_node = next_node
result = result.next_node
if a:
result.next_node = a
elif b:
result.next_node = b
else:
result.next_node = None
return head
# Tests
from linked_list import ListNode
a = ListNode(2)
a.next_node = ListNode(5)
a.next_node.next_node = ListNode(7)
b = ListNode(3)
b.next_node = ListNode(11)
r = merge(a, b)
print r.traversal()
# Time: 15 minutes
###
# Mistakes / Bugs / Misses
###
# Spent a long time looking for a bug here, when it was a bug in my library code.
