go: add «2130. Maximum Twin Sum of a Linked List»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/maximum-twin-sum-of-a-linked-list.go

@@ -0,0 +1,27 @@
+package main
+
+func pairSum(head *ListNode) int {
+	findMidAndBuild := func() ([]int, *ListNode) {
+		stack := make([]int, 0)
+
+		slow, fast := head, head
+		for fast != nil {
+			stack = append(stack, slow.Val)
+			slow, fast = slow.Next, fast.Next.Next
+		}
+
+		return stack, slow
+	}
+
+	stack, node := findMidAndBuild()
+
+	foundMax, idx := 0, len(stack)-1
+	for node != nil {
+		foundMax = max(foundMax, stack[idx]+node.Val)
+
+		node = node.Next
+		idx--
+	}
+
+	return foundMax
+}