1721. Swapping Nodes in a Linked List

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LeetCode

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Problem

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]

Code

class Solution {
    public ListNode swapNodes(ListNode head, int k) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        
        ListNode curr = dummy;
        ListNode start = dummy;
        
        for(int i = 0; i < k; i++) {
            start = start.next;
            curr = curr.next;
        }
        
        ListNode end = dummy;
        while(curr != null) {
            curr = curr.next;
            end = end.next;
        }
        
        int temp = start.val;
        start.val = end.val;
        end.val = temp;
        return dummy.next;
    }
}