head, tail = None, None
while l1 and l2:
if (l1.val < l2.val):
head, tail = insertTo(head, tail, l1.val)
l1 = l1.next
else:
head, tail = insertTo(head, tail, l2.val)
l2 = l2.next
if l1:
while l1:
head, tail = insertTo(head, tail, l1.val)
l1 = l1.next
if l2:
while l2:
head, tail = insertTo(head, tail, l2.val)
l2 = l2.next
return head
if __name__ == '__main__':
list1 = [1, 2]
list2 = [1, 2, 3, 4]
l1 = LinkedList.build_ll_from_list(list1)
l2 = LinkedList.build_ll_from_list(list2)
merged_head = solution(l1.head, l2.head)
merged = LinkedList(merged_head)
merged.print_ll()
from data_structures.linked_list import LinkedList
def find_len(head):
length = 0
while head:
length += 1
head = head.next
return length
def stack_solution(head):
stack = []
length = find_len(head)
if length == 0 or length == 1:
return True
i = 0
while i < length:
if i < (length//2):
stack.append(head.val)
head = head.next
else:
if head.val == stack[-1]:
stack.pop()
head = head.next
i += 1
return not stack
if __name__ == '__main__':
ll = LinkedList.build_ll_from_list([1, 2, 3, 2, 1])
print(stack_solution(ll.head))
# Reverse Linked List
# Reverse a singly linked list.
from data_structures.linked_list import LinkedList
def solution(ll):
prev = None
cur = ll.head
if not cur:
return ll
while cur:
tmp = cur.next
cur.next = prev
prev = cur
cur = tmp
return LinkedList(prev)
if __name__ == '__main__':
l = [1, 2, 3, 4]
ll = LinkedList.build_ll_from_list(l)
print("Before: ")
ll.print_ll()
reversed_ll = solution(ll)
print("After: ")
reversed_ll.print_ll()
