Package g2101_2200.s2130_maximum_twin_sum_of_a_linked_list

Class Solution

  • public class Solution
extends Object
    2130 - Maximum Twin Sum of a Linked List.

    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.

    Example 1:

    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:

    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:

    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, 105].
    • 1 <= Node.val <= 105

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • pairSum

        public int pairSum​(ListNode head)