[Solved] Given the head of a singly linked list and two integers left and right where left <= right, reverse the nodes of the list from position left to position right, and return the reversed list.

Question

Given the head of a singly linked list and two integers left and right where left <= right, reverse the nodes of the list from position left to position right, and return the reversed list.

Example 1:

Machine Learning Projects
Input: head = [1,2,3,4,5], left = 2, right = 4
Output: [1,4,3,2,5]

Example 2:

Input: head = [5], left = 1, right = 1
Output: [5]

Constraints:

  • The number of nodes in the list is n.
  • 1 <= n <= 500
  • -500 <= Node.val <= 500
  • 1 <= left <= right <= n

Follow up: Could you do it in one pass?

Python Solution

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def reverseBetween(self, head: ListNode, left: int, right: int) -> ListNode:
        dummy = ListNode(0)
        dummy.next = head
        
        leftportion = dummy
        
        for _ in range(left-1):
            leftportion = leftportion.next
        
        
        curr = leftportion.next
        x = curr
        prev = None
        
        for _ in range(right-left+1):
            nex = curr.next
            curr.next = prev
            prev,curr = curr,nex
        
        leftportion.next = prev
        x.next = nex
        return dummy.next
Abhishek Sharma
Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

Articles: 514

Leave a Reply

Your email address will not be published. Required fields are marked *