Add solution #2130

Author: JoshCrozier

README.md

@@ -393,6 +393,7 @@
 2114|[Maximum Number of Words Found in Sentences](./2114-maximum-number-of-words-found-in-sentences.js)|Easy|
 2116|[Check if a Parentheses String Can Be Valid](./2116-check-if-a-parentheses-string-can-be-valid.js)|Medium|
 2129|[Capitalize the Title](./2129-capitalize-the-title.js)|Easy|
+2130|[Maximum Twin Sum of a Linked List](./2130-maximum-twin-sum-of-a-linked-list.js)|Medium|
 2154|[Keep Multiplying Found Values by Two](./2154-keep-multiplying-found-values-by-two.js)|Easy|
 2185|[Counting Words With a Given Prefix](./2185-counting-words-with-a-given-prefix.js)|Easy|
 2215|[Find the Difference of Two Arrays](./2215-find-the-difference-of-two-arrays.js)|Easy|

solutions/2130-maximum-twin-sum-of-a-linked-list.js

@@ -0,0 +1,41 @@
+/**
+ * 2130. Maximum Twin Sum of a Linked List
+ * https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/
+ * Difficulty: Medium
+ *
+ * In a linked list of size n, where n is even, the ith node (0-indexed) of the linked list is known
+ * as the twin of the (n-1-i)th node, if 0 <= i <= (n / 2) - 1.
+ *
+ * For example, if n = 4, then node 0 is the twin of node 3, and node 1 is the twin of node 2. These
+ * are the only nodes with twins for n = 4.
+ *
+ * The twin sum is defined as the sum of a node and its twin.
+ *
+ * Given the head of a linked list with even length, return the maximum twin sum of the linked list.
+ */
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {number}
+ */
+var pairSum = function(head) {
+  const stack = [];
+  while (head) {
+    stack.push(head.val);
+    head = head.next;
+  }
+
+  let max = 0;
+  for (let i = 0; i < stack.length; i++) {
+    max = Math.max(max, stack[i] + stack[stack.length - 1 - i]);
+  }
+
+  return max;
+};