# 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: 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: 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 `[3, 2 * 105]`.
• `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`.

### 解題   Runtime: 332 ms, faster than 100%
Memory Usage: 15.2 MB, less than 84.69%
/**
* type ListNode struct {
* Val int
* Next *ListNode
* }
*/