4July2024 - 2181. Merge Nodes in Between Zeros.py

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def mergeNodes(self, head: Optional[ListNode]) -> Optional[ListNode]:
        dummy = ListNode(0)
        current = dummy
        node = head.next 
        segment_sum = 0 
        
        while node:
            if node.val != 0:
                segment_sum += node.val
            else:
                if segment_sum != 0:
                    current.next = ListNode(segment_sum)
                    current = current.next
                    segment_sum = 0
            node = node.next
        
        return dummy.next