/// <summary>
/// Merge two sorted linked lists and return it as a new list.
/// The new list should be made by splicing together the nodes of the first two lists.
/// Ex:
/// Input: 1->2->4, 1->3->4
/// </summary>
/// <param name="l1"></param>
/// <param name="l2"></param>
/// <returns></returns>
public static LeetCodeListNode MergeTwoLists(LeetCodeListNode l1, LeetCodeListNode l2)
{
LeetCodeListNode curr = null, head = null, next = null;// = new ListNode();
while (l1 != null || l2 != null)
{
if (l1?.val > l2?.val)
{
next = new LeetCodeListNode(l1.val);
l1 = l1.next;
}
else
{
next = new LeetCodeListNode(l2.val);
l2 = l2.next;
}
if (head == null)
{
head = next;
curr = next;
}
else
{
curr.next = next;
curr = curr.next;
}
}
return(l1);
}
/// <summary>
/// You are given two non-empty linked lists representing two
/// non-negative integers.The digits are stored in reverse order
/// and each of their nodes contain a single digit.Add the two
/// numbers and return it as a linked list.
/// You may assume the two numbers do not contain any leading zero,
/// except the number 0 itself.
///
/// Example:
/// Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
/// Output: 7 -> 0 -> 8
/// Explanation: 342 + 465 = 807.
/// </summary>
/// <param name="l1"></param>
/// <param name="l2"></param>
/// <returns></returns>
public static LeetCodeListNode AddTwoNumbers(LeetCodeListNode l1, LeetCodeListNode l2)
{
int carryOver = 0;
var sum = l1.val + l2.val;
if (sum > 9)
{
carryOver++;
sum %= 10;
}
LeetCodeListNode head = new LeetCodeListNode(sum);
AddTwoNumbers(l1?.next, l2?.next, carryOver, head);
return(head);
}
private static void AddTwoNumbers(LeetCodeListNode l1, LeetCodeListNode l2, int carry, LeetCodeListNode prevNode)
{
if (l2 == null && l1 == null && carry == 0)
{
return;
}
var sum = (l1 == null ? 0 : l1.val) + (l2 == null ? 0 : l2.val) + carry;
if (sum > 9)
{
carry = 1;
sum %= 10;
}
else
{
carry = 0;
}
var next = new LeetCodeListNode(sum);
prevNode.next = next;
AddTwoNumbers(l1?.next, l2?.next, carry, next);
}
