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 theheadof 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 [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.
Solutions
Solution 1
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# Definition for singly-linked list.# class ListNode:# def __init__(self, val=0, next=None):# self.val = val# self.next = nextclassSolution:defmergeNodes(self,head:Optional[ListNode])->Optional[ListNode]:dummy=tail=ListNode()s=0cur=head.nextwhilecur:ifcur.val!=0:s+=cur.valelse:tail.next=ListNode(s)tail=tail.nexts=0cur=cur.nextreturndummy.next
/** * Definition for singly-linked list. * type ListNode struct { * Val int * Next *ListNode * } */funcmergeNodes(head*ListNode)*ListNode{dummy:=&ListNode{}tail:=dummys:=0forcur:=head.Next;cur!=nil;cur=cur.Next{ifcur.Val!=0{s+=cur.Val}else{tail.Next=&ListNode{Val:s}tail=tail.Nexts=0}}returndummy.Next}