using System;

class Program
{
    public static void Main(string[] args)
    {
        int[,] sudokuPuzzle = {
            {5, 3, 0, 0, 7, 0, 0, 0, 0},
            {6, 0, 0, 1, 9, 5, 0, 0, 0},
            {0, 9, 8, 0, 0, 0, 0, 6, 0},
            {8, 0, 0, 0, 6, 0, 0, 0, 3},
            {4, 0, 0, 8, 0, 3, 0, 0, 1},
            {7, 0, 0, 0, 2, 0, 0, 0, 6},
            {0, 6, 0, 0, 0, 0, 2, 8, 0},
            {0, 0, 0, 4, 1, 9, 0, 0, 5},
            {0, 0, 0, 0, 8, 0, 0, 7, 9}
        };

        SolveSudoku(sudokuPuzzle, 0, 0);
        PrintSudoku(sudokuPuzzle);
    }

    public static void PrintSudoku(int[,] puzzle)
    {
        Console.WriteLine("+-----+-----+-----+");

        for (int i = 0; i < 9; ++i)
        {
            for (int j = 0; j < 9; ++j)
                Console.Write("|{0}", puzzle[i, j]);

            Console.WriteLine("|");
            if ((i + 1) % 3 == 0) Console.WriteLine("+-----+-----+-----+");
        }
    }

    public static bool SolveSudoku(int[,] puzzle, int row, int col)
    {
        if (row < 9 && col < 9)
        {
            if (puzzle[row, col] != 0)
            {
                if ((col + 1) < 9) return SolveSudoku(puzzle, row, col + 1);
                else if ((row + 1) < 9) return SolveSudoku(puzzle, row + 1, 0);
                else return true;
            }
            else
            {
                for (int i = 0; i < 9; ++i)
                {
                    if (IsAvailable(puzzle, row, col, i + 1))
                    {
                        puzzle[row, col] = i + 1;

                        if ((col + 1) < 9)
                        {
                            if (SolveSudoku(puzzle, row, col + 1)) return true;
                            else puzzle[row, col] = 0;
                        }
                        else if ((row + 1) < 9)
                        {
                            if (SolveSudoku(puzzle, row + 1, 0)) return true;
                            else puzzle[row, col] = 0;
                        }
                        else return true;
                    }
                }
            }

            return false;
        }
        else return true;
    }

    private static bool IsAvailable(int[,] puzzle, int row, int col, int num)
    {
        int rowStart = (row / 3) * 3;
        int colStart = (col / 3) * 3;

        for (int i = 0; i < 9; ++i)
        {
            if (puzzle[row, i] == num) return false;
            if (puzzle[i, col] == num) return false;
            if (puzzle[rowStart + (i % 3), colStart + (i / 3)] == num) return false;
        }

        return true;
    }
}

C Sharp Online Compiler

Write, Run & Share C# code online using OneCompiler's C# online compiler for free. It's one of the robust, feature-rich online compilers for C# language, running on the latest version 8.0. Getting started with the OneCompiler's C# compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C# and start coding.

Read inputs from stdin

OneCompiler's C# online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

using System;
 
namespace Sample
{
  class Test
    {
      public static void Main(string[] args)
       {
         string name;
         name = Console.ReadLine();
         Console.WriteLine("Hello {0} ", name);
	}
     }
}

About C Sharp

C# is a general purpose object-oriented programming language by Microsoft. Though initially it was developed as part of .net but later it was approved by ECMA and ISO standards.

You can use C# to create variety of applications, like web, windows, mobile, console applications and much more using Visual studio.

Syntax help

Data types

Data TypeDescriptionRangesize
intTo store integers-2,147,483,648 to 2,147,483,6474 bytes
doubleto store large floating point numbers with decimalscan store 15 decimal digits8 bytes
floatto store floating point numbers with decimalscan store upto 7 decimal digits4 bytes
charto store single characters-2 bytes
stringto stores text-2 bytes per character
boolto stores either true or false-1 bit

Variables

Syntax

datatype variable-name = value;

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition or set of few conditions IF-ELSE is used.

if(conditional-expression) {
   // code
} 
else {
   // code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement) {
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

data-type[] array-name;

Methods

Method is a set of statements which gets executed only when they are called. Call the method name in the main function to execute the method.

Syntax

static void method-name() 
{
  // code to be executed
}