‘Swap Nodes in Pairs (Medium)

📌 Problem

https://leetcode.com/problems/swap-nodes-in-pairs/

📌 Answer

• Iterative ```java /**
• Definition for singly-linked list.
• public class ListNode {
• int val;
• ListNode next;
• ListNode() {}
• ListNode(int val) { this.val = val; }
• ListNode(int val, ListNode next) { this.val = val; this.next = next; }

• } */ class Solution { public ListNode swapPairs(ListNode head) {

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  ListNode temp = head; while (head != null && head.next != null) { int curr = head.val; int next = head.next.val; head.next.val = curr; head.val = next; head = head.next.next; } return temp; } } ```

• Recursive
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  class Solution { public ListNode swapPairs(ListNode head) { if (head == null || head.next == null) return head; ListNode nxt = head.next; head.next = swapPairs(nxt.next); nxt.next = head; return nxt; } }

• Reference
  • https://leetcode.com/problems/swap-nodes-in-pairs/solutions/11204/java-recursive-and-iterative-solutions/?orderBy=most_votes&languageTags=java