You are given the head
of a linked list, and an integer k
.
Return the head of the linked list after swapping the values of the kth
node from the beginning and the kth
node from the end (the list is 1-indexed).
Example 1:
Input: head = [1,2,3,4,5], k = 2
Output: [1,4,3,2,5]
Example 2:
Input: head = [7,9,6,6,7,8,3,0,9,5], k = 5
Output: [7,9,6,6,8,7,3,0,9,5]
Constraints:
- The number of nodes in the list is
n
. -
1 <= k <= n <= 105
-
0 <= Node.val <= 100
SOLUTION:
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class Solution:
def lenList(self, head, a, k):
if head:
curr = 1 + self.lenList(head.next, a + 1, k)
if a == k:
self.a = head
if curr == k:
self.b = head
return curr
return 0
def swapNodes(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
n = self.lenList(head, 1, k)
self.a.val, self.b.val = self.b.val, self.a.val
return head
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