2130. Maximum Twin Sum of a Linked List

Author: a-khakimov

leetcode-scala/src/main/scala/LeetCode75/Linked_List/2130. Maximum Twin Sum of a Linked List.sc

@@ -0,0 +1,57 @@
+import scala.annotation.tailrec
+
+/**
+ * Definition for singly-linked list.
+ * class ListNode(_x: Int = 0, _next: ListNode = null) {
+ *   var next: ListNode = _next
+ *   var x: Int = _x
+ * }
+ */
+
+class ListNode(_x: Int = 0, _next: ListNode = null) {
+  var next: ListNode = _next
+  var x: Int = _x
+}
+
+object Solution {
+
+  def pairSum(head: ListNode): Int = {
+    val stack = scala.collection.mutable.Stack.empty[Int]
+    var it = head
+    while (it != null) {
+      stack.push(it.x)
+      it = it.next
+    }
+    val hlen = stack.length / 2
+    var i = 0
+    var answer = 0
+    it = head
+    while (i < hlen) {
+      answer = Math.max(answer, it.x + stack.pop())
+      it = it.next
+      i += 1
+    }
+    answer
+  }
+
+  def pprint(head: ListNode): Unit = {
+    @tailrec def go(node: ListNode, i: Int): Unit = {
+      print(s"[$i]=${node.x}, ")
+      if (node.next == null) ()
+      else go(node.next, i + 1)
+    }
+
+    go(head, 0)
+  }
+}
+
+
+// val list = ListNode(5, ListNode(4, ListNode(2, ListNode(1))))
+val list = ListNode(47, ListNode(22, ListNode(81, ListNode(46, ListNode(90, ListNode(92, ListNode(9, ListNode(81, ListNode(5, ListNode(9))))))))))
+
+//47,22,81,46,94,95,90,22,55,91,6,83,49,65,10,32,41,26,83,99,14,85,42,99,89,69,30,
+//9  5, 81, 9,74,32,92,
+
+Solution.pprint(list)
+Solution.pairSum(list)
+Solution.pprint(list)