Syntax error Program to merge in between linked lists in Python

Program to merge in between linked lists in Python

Suppose we have two linked lists L1 and L2 of length m and n respectively, we also have two positions a and b. We have to remove nodes from L1 from a-th node to node b-th node and merge L2 in between.

So, if the input is like L1 = [1,5,6,7,1,6,3,9,12] L2 = [5,7,1,6] a = 3 b = 6, then the output will be [1, 5, 6, 5, 7, 1, 6, 9, 12]

To solve this, we will follow these steps −

  • head2 := L2, temp := L2
  • while temp has next node, do
    • temp := next of temp
  • tail2 := temp
  • count := 0
  • temp := L1
  • end1 := null, start3 := null
  • while temp is not null, do
    • if count is same as a-1, then
      • end1 := temp
    • if count is same as b+1, then
      • start3 := temp
      • come out from loop
    • temp := next of temp
    • count := count + 1
  • next of end1 := head2
  • next of tail2 := start3
  • return L1

Example

Let us see the following implementation to get better understanding −

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

def make_list(elements):
   head = ListNode(elements[0])
   for element in elements[1:]:
      ptr = head
      while ptr.next:
         ptr = ptr.next
      ptr.next = ListNode(element)
   return head

def print_list(head):
   ptr = head
   print('[', end = "")
   while ptr:
      print(ptr.val, end = ", ")
      ptr = ptr.next
   print(']')

def solve(L1, L2, a, b):
   head2 = temp = L2
   while temp.next:
      temp = temp.next
   tail2 = temp

   count = 0
   temp = L1
   end1, start3 = None, None
   while temp:
      if count == a-1:
         end1 = temp
      if count == b+1:
         start3 = temp
         break
      temp = temp.next
      count += 1

   end1.next = head2
   tail2.next = start3
   return L1

L1 = [1,5,6,7,1,6,3,9,12]
L2 = [5,7,1,6]
a = 3
b = 6
print_list(solve(make_list(L1), make_list(L2), a, b))

Input

[1,5,6,7,1,6,3,9,12], [5,7,1,6], 3, 6

Output

[1, 5, 6, 5, 7, 1, 6, 9, 12, ]
Updated on: 2021-10-05T13:11:11+05:30

970 Views

Kickstart Your Career

Get certified by completing the course

Get Started
Advertisements