2181.go

// Source: https://leetcode.com/problems/merge-nodes-in-between-zeros
// Title: Merge Nodes in Between Zeros
// Difficulty: Medium
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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:
//
//   https://assets.leetcode.com/uploads/2022/02/02/ex1-1.png
//
//   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:
//
//   https://assets.leetcode.com/uploads/2022/02/02/ex2-1.png
//
//   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 * 10^5].
//   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.
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package main

// Definition for singly-linked list.
type ListNode struct {
	Val  int
	Next *ListNode
}

// Sum values to the zero-node before it
func mergeNodes(head *ListNode) *ListNode {
	curr, zero := head.Next, head

	for curr.Next != nil {
		if curr.Val == 0 {
			zero.Next = curr
			zero = curr
		}
		zero.Val += curr.Val
		curr = curr.Next
	}
	zero.Next = nil
	return head
}