ADBlock is blocking some content on the site # Program to interleave list elements from two linked lists in Python

PythonServer Side ProgrammingProgramming

Suppose we have two linked lists l1 and l2, we have to return one linked list by interleaving elements of these two lists starting with l1. If there are any leftover nodes in a linked list, they should be appended to the list.

So, if the input is like l1 = [5,4,6,3,4,7] l2 = [8,6,9], then the output will be [5,8,4,6,6,9,3,4,7]

To solve this, we will follow these steps −

• ans := l1

• while l2 is not null, do

• if ans is not null, then

• if next of ans is not null, then

• newnode := a new list node with same value of l2

• next of newnode := next of ans

• next of ans := newnode

• ans := next of newnode

• l2 := next of l2

• otherwise,

• next of ans := l2

• come out from the loop

• otherwise,

• return l2

• return l1

Let us see the following implementation to get better understanding −

## Example

```Source Code (Python):
class ListNode:
def __init__(self, data, next = None):
self.val = data
self.next = next

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

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

class Solution:
def solve(self, l1, l2):
ans = l1
while l2:
if ans:
if ans.next != None:
newnode = ListNode(l2.val, None)
newnode.next = ans.next
ans.next = newnode
ans = newnode.next
l2 = l2.next
else:
ans.next = l2
break
else:
return l2
return l1

ob = Solution()
l1 = make_list([5,4,6,3,4,7])
l2 = make_list([8,6,9])
res = ob.solve(l1,l2)
print_list(res)```

## Input

`[5,4,6,3,4,7],[8,6,9]`

## Output

`[5, 8, 4, 6, 6, 9, 3, 4, 7, ]`