Merge pull request neetcode-gh#905 from pontusdacke/128-Longest-Consecutive-Sequence

Add csharp solution for 128 Longest Consecutive Sequence

Author: Ahmad-A0

csharp/128-Longest-Consecutive-Sequence.cs

@@ -0,0 +1,22 @@
+public class Solution {
+    public int LongestConsecutive(int[] nums) {
+        if (nums.Length < 2) return nums.Length;
+        
+        var set = new HashSet<int>(nums);
+        var longest = 0;
+        foreach (var n in set)
+        {
+            if (!set.Contains(n-1))
+            {
+                var length = 0;
+                while (set.Contains(n+length))
+                {
+                    length++;
+                    longest = Math.Max(longest, length);
+                }
+            }
+        }
+        
+        return longest;
+    }
+}