LeetCode: Add Two Numbers (Solution)

Link to the description of the task: https://leetcode.com/problems/add-two-numbers/

	public class ListNode
	{
	public int val;
	public ListNode next;

	public ListNode(int val = 0, ListNode next = null)
	{
	this.val = val;
	this.next = next;
	}
	}

	public class Solution
	{
	public ListNode AddTwoNumbers(ListNode firstListNode, ListNode secondListNode)
	{
	var currentNodes = (first: firstListNode, second: secondListNode);
	var carry = 0;

	var resultFirstNode = SumNodes(currentNodes, ref carry);

	var resultLastNode = resultFirstNode;

	while (TryMoveForward(ref currentNodes))
	{
	Extend(ref resultLastNode, SumNodes(currentNodes, ref carry));
	}

	if (carry > 0)
	{
	Extend(ref resultLastNode, new ListNode(carry));
	}

	return resultFirstNode;
	}

	private static bool HaveComeToEnd((ListNode first, ListNode second) nodes) =>
	nodes.first is null && nodes.second is null;

	private static void Extend(ref ListNode node, ListNode extension)
	{
	node.next = extension;
	node = node.next;
	}

	private static bool TryMoveForward(ref (ListNode first, ListNode second) currentNodes)
	{
	currentNodes.first = currentNodes.first?.next;
	currentNodes.second = currentNodes.second?.next;

	return !HaveComeToEnd(currentNodes);
	}

	private static ListNode SumNodes((ListNode first, ListNode second) nodes, ref int carry)
	{
	var firstDigit = nodes.first is null ? 0 : nodes.first.val;
	var secondDigit = nodes.second is null ? 0 : nodes.second.val;

	var sum = SumDigits(firstDigit, secondDigit, ref carry);

	return new ListNode(sum);
	}

	private static int SumDigits(int first, int second, ref int carry)
	{
	var total = first + second + carry;
	var sum = total % 10;
	carry = (total - sum) / 10;

	return sum;
	}
	}

view raw LeetCodeAddTwoNumbers.cs hosted with

by GitHub

Conclusion:

It looks pretty nice!

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