Problem statement

https://binarysearch.com/problems/Insert-Into-Linked-List/

Solution

Just do what is asked, add dummy variable in the beginning.

Complexity

It is O(n) for time and space.

Code

class Solution:
    def solve(self, head, pos, val):
        dummy = LLNode(-1)
        dummy.next = head

        curr = dummy
        for _ in range(pos):
            curr = curr.next

        nxt = curr.next
        curr.next = LLNode(val)
        curr.next.next = nxt

        return dummy.next