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merge-nodes-between-zeroes.dart (1258B)

      1 //Merge the values contained between zeroes and return the new linked list.
      2 //Ex. 0 1 2 0 2 2 2 2 0
      3 //Output [3, 8]
      4 //Explanation: Adding 1 and 2 between the first two zeroes gives us 3
      5 //then adding 2 4 times gives eight.
      6 //The time complexity of this code is O(n) where n is the number 
      7 //of nodes in the inputted list.
      8 //Time: 569ms Beats: 50%
      9 //Memory: 229.9MB Beats: 16.67%
     10 
     11 
     12 /**
     13  * Definition for singly-linked list.
     14  * class ListNode {
     15  *   int val;
     16  *   ListNode? next;
     17  *   ListNode([this.val = 0, this.next]);
     18  * }
     19  */
     20 class Solution {
     21   ListNode? mergeNodes(ListNode? head) {
     22 
     23       ListNode? start;
     24       ListNode? last;
     25       head = head?.next;
     26       int total = 0;
     27       while(head != null){
     28           if(head.val == 0){
     29               if(start == null){
     30                   start = new ListNode();
     31                   start.val = total;
     32                   total = 0;
     33                   last = start;
     34               }
     35               else{
     36                   ListNode current = new ListNode();
     37                   current.val = total;
     38                   last?.next = current;
     39                   last = current;
     40                   total = 0;
     41               }
     42           }
     43           total += head.val;
     44           head = head.next;
     45       }
     46       return start;
     47   }
     48 }