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:
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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:
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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 [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%
/**
* Definition for singly-linked list.
* type ListNode struct {
* Val int
* Next *ListNode
* }
*/
func mergeNodes(head *ListNode) *ListNode {
cur, pre := head.Next, head
​
for cur.Next != nil {
if cur.Val == 0 {
pre.Next = cur
pre = cur
}
pre.Val += cur.Val
cur = cur.Next
}
​
pre.Next = nil
​
return head
}