2130. Maximum Twin Sum of a Linked List: RETRY

Author: tan-wei

src/solution/mod.rs

@@ -1608,3 +1608,4 @@ mod s2125_number_of_laser_beams_in_a_bank;
 mod s2126_destroying_asteroids;
 mod s2127_maximum_employees_to_be_invited_to_a_meeting;
 mod s2129_capitalize_the_title;
+mod s2130_maximum_twin_sum_of_a_linked_list;

src/solution/s2130_maximum_twin_sum_of_a_linked_list.rs

@@ -0,0 +1,109 @@
+/**
+ * [2130] Maximum Twin Sum of a Linked List
+ *
+ * In a linked list of size n, where n is even, the i^th 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.
+ *  
+ * Example 1:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/12/03/eg1drawio.png" style="width: 250px; height: 70px;" />
+ * Input: head = [5,4,2,1]
+ * Output: 6
+ * Explanation:
+ * Nodes 0 and 1 are the twins of nodes 3 and 2, respectively. All have twin sum = 6.
+ * There are no other nodes with twins in the linked list.
+ * Thus, the maximum twin sum of the linked list is 6.
+ *
+ * Example 2:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/12/03/eg2drawio.png" style="width: 250px; height: 70px;" />
+ * Input: head = [4,2,2,3]
+ * Output: 7
+ * Explanation:
+ * The nodes with twins present in this linked list are:
+ * - Node 0 is the twin of node 3 having a twin sum of 4 + 3 = 7.
+ * - Node 1 is the twin of node 2 having a twin sum of 2 + 2 = 4.
+ * Thus, the maximum twin sum of the linked list is max(7, 4) = 7.
+ *
+ * Example 3:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/12/03/eg3drawio.png" style="width: 200px; height: 88px;" />
+ * Input: head = [1,100000]
+ * Output: 100001
+ * Explanation:
+ * There is only one node with a twin in the linked list having twin sum of 1 + 100000 = 100001.
+ *
+ *  
+ * Constraints:
+ *
+ * 	The number of nodes in the list is an even integer in the range [2, 10^5].
+ * 	1 <= Node.val <= 10^5
+ *
+ */
+pub struct Solution {}
+use crate::util::linked_list::{to_list, ListNode};
+
+// problem: https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/
+// discuss: https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+// Definition for singly-linked list.
+// #[derive(PartialEq, Eq, Clone, Debug)]
+// pub struct ListNode {
+//   pub val: i32,
+//   pub next: Option<Box<ListNode>>
+// }
+//
+// impl ListNode {
+//   #[inline]
+//   fn new(val: i32) -> Self {
+//     ListNode {
+//       next: None,
+//       val
+//     }
+//   }
+// }
+impl Solution {
+    pub fn pair_sum(head: Option<Box<ListNode>>) -> i32 {
+        0
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    #[ignore]
+    fn test_2130_example_1() {
+        let head = linked![5, 4, 2, 1];
+
+        let result = 6;
+
+        assert_eq!(Solution::pair_sum(head), result);
+    }
+
+    #[test]
+    #[ignore]
+    fn test_2130_example_2() {
+        let head = linked![4, 2, 2, 3];
+
+        let result = 7;
+
+        assert_eq!(Solution::pair_sum(head), result);
+    }
+
+    #[test]
+    #[ignore]
+    fn test_2130_example_3() {
+        let head = linked![1, 100000];
+
+        let result = 100001;
+
+        assert_eq!(Solution::pair_sum(head), result);
+    }
+}