Program to find linked list intersection from two linked list in Python

Suppose we have two sorted linked lists L1 and L2, we have to make a new sorted linked list which contains the intersection of these two lists.

So, if the input is like L1 = [2, 4, 8] L2 = [3, 4, 8, 10], then the output will be [4, 8, ]

To solve this, we will follow these steps −

• head := a new node with value 0
• cur := head
• while l1 and l2 are not empty, do
  • if value of l1 < value of l2, then
    • l1 := next of l1
  • otherwise when value of l2 < value of l1, then
    • l2 := next of l2
  • otherwise,
    • next of cur := a new node with value same as value of l1
    • l1 := next of l1
    • l2 := next of l2
    • cur := next of cur
• return next of head

Let us see the following implementation to get better understanding −

Example

 Live Demo

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(']')
class Solution:
   def solve(self, l1, l2):
      head = cur = ListNode(0)
      while l1 and l2:
         if l1.val < l2.val:
            l1 = l1.next
         elif l2.val < l1.val:
            l2 = l2.next
         else:
            cur.next = ListNode(l1.val)
            l1 = l1.next
            l2 = l2.next
            cur = cur.next
      return head.next
ob = Solution()
L1 = make_list([2, 4, 8])
L2 = make_list([3, 4, 8, 10])
print_list(ob.solve(L1, L2))

Input

[2, 4, 8], [3, 4, 8, 10]

Output

[4, 8, ]