add solution for 'AddTwoNumbers' task

Author: nMykhailenko

C#/LeetCodeResolves/LeetCodeResolves/AddTwoNumbers/ListNode.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace LeetCodeResolves.AddTwoNumbers
+{
+    public class ListNode
+    {
+        public int value;
+        public ListNode next;
+        public ListNode(int  value = 0, ListNode next = null)
+        {
+            this.value = value;
+            this.next = next;
+        }
+    }
+}

C#/LeetCodeResolves/LeetCodeResolves/AddTwoNumbers/Program.cs

@@ -0,0 +1,69 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace LeetCodeResolves.AddTwoNumbers
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            var fNode = new ListNode
+            {
+                value = 2,
+                next = new ListNode
+                {
+                    value = 4,
+                    next = new ListNode
+                    {
+                        value = 3,
+                        next = null
+                    }
+                }
+            };
+
+            var sNode = new ListNode
+            {
+                value = 5,
+                next = new ListNode
+                {
+                    value = 6,
+                    next = new ListNode
+                    {
+                        value = 4,
+                        next = null
+                    }
+                }
+            };
+
+            var result = AddTwoNumbers(fNode, sNode);
+
+            Console.ReadLine();
+        }
+
+        static ListNode AddTwoNumbers(ListNode l1, ListNode l2)
+        {
+            var dummyHead = new ListNode(0);
+            ListNode p = l1, q = l2, current = dummyHead;
+            var carry = 0;
+            while(p != null || q != null)
+            {
+                var x = p != null ? p.value : 0;
+                var y = q != null ? q.value : 0;
+                var sum = carry + x + y;
+                carry = sum / 10;
+                current.next = new ListNode(sum % 10);
+                current = current.next;
+                if (p != null) p = p.next;
+                if (q != null) q = q.next;
+            }
+
+            if(carry > 0)
+            {
+                current.next = new ListNode(carry);
+            }
+
+            return dummyHead.next;
+        }
+    }
+}

C#/LeetCodeResolves/LeetCodeResolves/LeetCodeResolves.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp3.1</TargetFramework>
-    <StartupObject>LeetCodeResolves.TwoSum.Program</StartupObject>
+    <StartupObject>LeetCodeResolves.AddTwoNumbers.Program</StartupObject>
   </PropertyGroup>
 
 </Project>