BinarySearch 0435 Reverse an Inner Linked List

Problem statement

https://binarysearch.com/problems/Reverse-an-Inner-Linked-List/

Solution

Equal to Leetcode 0092. Reverse Linked List II.

Complexity

It is O(n) for time and O(1) for space.

Code

class Solution:
    def solve(self, head, m, n):
        m, n = m + 1, n + 1
        if m == n: return head
        dummy = LLNode(0)
        dummy.next = head
        pre = dummy
        for i in range(m-1):
            pre = pre.next
            
        curr = pre.next
        nxt = curr.next
        
        for i in range(n-m):
            tmp = nxt.next
            nxt.next = curr
            curr = nxt
            nxt = tmp
            
        pre.next.next = nxt
        pre.next = curr
        return dummy.next