diff --git a/.gitignore b/.gitignore
deleted file mode 100644
index 982c407..0000000
--- a/.gitignore
+++ /dev/null
@@ -1,6 +0,0 @@
-# Ignore everything
-*
-
-# But not these files...
-!.cs
-!.gitignore
\ No newline at end of file
diff --git a/36.cs b/36.cs
new file mode 100644
index 0000000..cf4e3f8
--- /dev/null
+++ b/36.cs
@@ -0,0 +1,57 @@
+public class Solution
+{
+    public static bool IsValidSudoku(char[][] sudokuBoard)
+    {
+        var rows = new Dictionary<int, HashSet<char>>();
+        var columns = new Dictionary<int, HashSet<char>>();
+        var box = new Dictionary<(int row, int col), HashSet<char>>();
+
+        for (int i = 0; i < 9; i++)
+        {
+            if (!rows.ContainsKey(i))
+            {
+                rows[i] = new HashSet<char>();
+            }
+            if (!columns.ContainsKey(i))
+            {
+                columns[i] = new HashSet<char>();
+            }
+        }
+
+        for (int i = 0; i < 9; i++)
+        {
+            for (int j = 0; j < 9; j++)
+            {
+                if (!box.ContainsKey((i / 3, j / 3)))
+                {
+                    box[(i / 3, j / 3)] = new HashSet<char>();
+                }
+            }
+        }
+
+        for (int i = 0; i < 9; i++)
+        {
+            for (int j = 0; j < 9; j++)
+            {
+                if (sudokuBoard[i][j] == '.') continue;
+
+                if (IsValid(sudokuBoard, rows, columns, box, i, j))
+                {
+                    rows[i].Add(sudokuBoard[i][j]);
+                    columns[j].Add(sudokuBoard[i][j]);
+                    box[(i / 3, j / 3)].Add(sudokuBoard[i][j]);
+                }
+                else
+                {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    private static bool IsValid(char[][] sudokuBoard, Dictionary<int, HashSet<char>> rows, Dictionary<int, HashSet<char>> columns, Dictionary<(int row, int col), HashSet<char>> box, int i, int j)
+    {
+        return !rows[i].Contains(sudokuBoard[i][j]) && !columns[j].Contains(sudokuBoard[i][j]) && !box[(i / 3, j / 3)].Contains(sudokuBoard[i][j]);
+    }
+}
\ No newline at end of file