24. Swap Nodes in Pairs

Author: Tushar Borole

.idea/workspace.xml

@@ -86,6 +86,7 @@
 | 3    | [Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)             | [Sliding Window Approach](longest_substring.js)                                                               | 84 ms            | 38.4 MB              | Medium     | O(N)            |                  | [:link:](https://www.youtube.com/watch?v=MK-NZ4hN7rs)             |
 | 137  | [Single Number II](https://leetcode.com/problems/single-number-ii/)                                                                         | [Iterative](single_number_II.js)                                                                              | 64 ms            | 37.6 MB              | Medium     | NlogN           |                  | [:link:](https://www.youtube.com/watch?v=KXjgQWDvQ24)             |
 | 11   | [Container With Most Water](https://leetcode.com/problems/container-with-most-water/)                                                       | [Ratcheting](container_with_most_water.js)                                                                    | 52 ms            | 35.4 MB              | Medium     | O(N)            | O(1)             | [:link:](https://www.youtube.com/watch?v=k5fbSqb9sCI&t=138s)      |
+| 24   | [Swap Nodes in Pairs](https://leetcode.com/problems/swap-nodes-in-pairs/)                                                                   | [Recursive](swap_nodes_in_pairs.js)                                                                           | 68 ms            | 34 MB                | Medium     | O(N)            |                  | [:link:](https://www.youtube.com/watch?v=zOovxGmION4)             |
 | 340  | [Longest Substring with At Most K Distinct Characters](https://leetcode.com/problems/longest-substring-with-at-most-k-distinct-characters/) | [Sliding Window Approach](k_distinct_characters.js)                                                           | 68 ms            | 37.1 MB              | Hard       | NlogN           |                  | [:link:](https://www.youtube.com/watch?v=MK-NZ4hN7rs&t=1936s)     |
 
 ## Others

README.md

@@ -0,0 +1,29 @@
+// https://leetcode.com/problems/swap-nodes-in-pairs/submissions/
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+var swapPairs = function(head) {
+  if (head === null || head.next === null) {
+    return head;
+  }
+
+  let node = head.next; //?
+  head.next = swapPairs(head.next.next); //4, 2
+  node.next = head;
+  return node;
+};
+
+let node = new ListNode(1);
+node.next = new ListNode(2);
+node.next.next = new ListNode(3);
+node.next.next.next = new ListNode(4);
+
+swapPairs(node); //?