diff --git a/leetcode/src/36.c b/leetcode/src/36.c
new file mode 100644
index 00000000..28aaa524
--- /dev/null
+++ b/leetcode/src/36.c
@@ -0,0 +1,69 @@
+/**
+ * Check if a Sudoku board is valid.
+ *
+ * The function takes a 2D character array representing the Sudoku board, the
+ * number of rows in the board (boardSize), and an array representing the number
+ * of columns in each row (boardColSize). It returns true if the Sudoku board is
+ * valid according to Sudoku rules, and false otherwise.
+ *
+ * Parameters:
+ * - board: A 2D character array representing the Sudoku board.
+ * - boardSize: The number of rows in the Sudoku board.
+ * - boardColSize: An array representing the number of columns in each row of
+ * the Sudoku board.
+ *
+ * Return:
+ * - true if the Sudoku board is valid, false otherwise.
+ */
+bool isValidSudoku(char** board, int boardSize, int* boardColSize)
+{
+    // Arrays to keep track of numbers encountered in rows, columns, and
+    // subgrids
+    int m[9][9] = {0};
+    int m_row[9][9] = {0};
+    int m_col[9][9] = {0};
+    int count;
+
+    // Iterate through each cell in the board
+    for (int i = 0; i < boardSize; i++)
+    {
+        if (i < 3)
+            count = 0;
+        else if (i > 2 && i < 6)
+            count = 3;
+        else if (i >= 6)
+            count = 6;
+
+        for (int j = 0; j < *boardColSize; j++)
+        {
+            // Check if the cell contains a valid digit (between '1' and '9')
+            if (board[i][j] >= '1' && board[i][j] <= '9')
+            {
+                int num = board[i][j] - '0';
+                m_row[i][num - 1]++;
+                m_col[j][num - 1]++;
+                m[count + j / 3][num - 1]++;
+            }
+        }
+        count = 0;
+    }
+
+    // Check for duplicate numbers in rows, columns, and subgrids
+    for (int i = 0; i < boardSize; i++)
+    {
+        for (int j = 0; j < *boardColSize; j++)
+        {
+            if (board[i][j] >= '1' && board[i][j] <= '9')
+            {
+                int num = board[i][j] - '0';
+                if (m_row[i][num - 1] > 1 || m_col[j][num - 1] > 1 ||
+                    m[(i / 3) * 3 + j / 3][num - 1] > 1)
+                {
+                    return false;
+                }
+            }
+        }
+    }
+
+    return true;
+}