2181 - Merge Nodes in Between Zeros\.

Medium

You are given the head of a linked list, which contains a series of integers separated by 0's. The beginning and end of the linked list will have Node.val == 0.

For every two consecutive 0's, merge all the nodes lying in between them into a single node whose value is the sum of all the merged nodes. The modified list should not contain any 0's.

Return the head of the modified linked list.

Example 1:

Input: head = 0,3,1,0,4,5,2,0

Output: 4,11

Explanation:

The above figure represents the given linked list. The modified list contains

• The sum of the nodes marked in green: 3 + 1 = 4.

• The sum of the nodes marked in red: 4 + 5 + 2 = 11.

Example 2:

Input: head = 0,1,0,3,0,2,2,0

Output: 1,3,4

Explanation:

The above figure represents the given linked list. The modified list contains

• The sum of the nodes marked in green: 1 = 1.

• The sum of the nodes marked in red: 3 = 3.

• The sum of the nodes marked in yellow: 2 + 2 = 4.

Constraints:

• The number of nodes in the list is in the range <code>3, 2 * 10⁵</code>.

• 0 <= Node.val <= 1000

• There are no two consecutive nodes with Node.val == 0.

• The beginning and end of the linked list have Node.val == 0.