using System;

using System.Collections.Generic;

using System.Linq;

// To execute C#, please define "static void Main" on a class

// named Solution.

/*

 Write a method that validates a sudoku puzzle.

 A sudoku puzzle is valid if all rows, columns, and 3x3 squares have distinct numbers 1-9 with no duplicates.

 https://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/Sudoku-by-L2G-20050714.svg/250px-Sudoku-by-L2G-20050714.svg.png

 Input: A list of lists

*/

​

class Solution

{

    static void Main(string[] args)

    {

        int? n = null;

        List<List<int?>> input = new List<List<int?>>()

        {

            new List<int?>() {5,3,n,n,7,n,n,n,n},

            new List<int?>() {6,n,n,1,9,5,n,n,n},

            new List<int?>() {n,9,8,n,n,n,n,6,n},

            new List<int?>() {8,n,n,n,6,n,n,n,3},

            new List<int?>() {4,n,n,8,n,3,n,n,1},

            new List<int?>() {7,n,n,n,2,n,n,n,6},

            new List<int?>() {n,6,n,n,n,n,2,8,n},

            new List<int?>() {n,n,n,4,1,9,n,n,5},

            new List<int?>() {n,n,n,n,8,n,n,7,9}

        };

​

        if (IsValidSudoku(input))

        {

            Console.WriteLine("Valid");

        }

        else

        {

            Console.WriteLine("Invalid");

        }

    }

​

    public static bool IsValidSudoku(List<List<int?>> input)

    {

        // Checking duplicates in the Rows

​

        foreach(var eachRow in input)

        {

            var rowAsArray = eachRow.Where(lst => lst != null).ToList();

            if(rowAsArray.Distinct().Count() != rowAsArray.Count())

            {

                return false;

            }

        }

​

        // Checking the duplicates in the columns

​

        List<List<int?>> columnBasedList = input.ToList();

​

        int rowCount = 0;

        int ColumCount = 0;

​

        foreach(var eachRow in input)

        {

            rowCount = 0;

​

            foreach(var eachColumn in input)

            {    

            //     new List<int?>() {5,3,n,n,7,n,n,n,n},

            //     new List<int?>() {6,n,n,1,9,5,n,n,n},

            // new List<int?>() {n,9,8,n,n,n,n,6,n},

            // new List<int?>() {8,n,n,n,6,n,n,n,3},

​

                columnBasedList[rowCount][ColumCount] = input[ColumCount][rowCount];

​

                // columnBasedList[0][0] = input[0][0]; = 5

                // columnBasedList[0][1] = input[1][0]; = 6

                // columnBasedList[0][2] = input[2][0]; = n

​

                // 5,6,n

​

                rowCount++;

            }

​

            ColumCount++;

        }

​

        foreach(var eachRow in columnBasedList)

        {

​

​

            var rowAsArray = eachRow.Where(lst => lst != null).ToList();

            if(rowAsArray.Distinct().Count() != rowAsArray.Count())

            {

                return false;

            }

        }

​

        return true;

​

    }

}

​