Chogo8Q

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;

namespace CSharp_Shell
{

    public static class Program
    {

        static void printBoard(string [, ] board) {
            for (int i = 0; i < 4; i++) {
                for (int j = 0; j < 4; j++) {
                    Console.Write(board[i, j] + " ");
                }
                Console.Write("\n");
            }
        }

        static bool checkIfSafe(string [,] board, int row, int col)
        {
          //check if all cols in current row are safe
          for(int i = col; i < 4; i++)
          {
             if(board[row, i] == "Q")
                {Console.WriteLine("This row is not safe");
                return false;}
          }

          //check all rows in current col
          for(int i = row; i < 4; i++)
          {
             if(board[i, col] == "Q"){
                Console.WriteLine("This col is not safe");
                return false;}
          }

          //check diagonals to the left\

          for(int i = row, j = col; i >= 0 && j >= 0; i--, j--)
          {
              if(board[i, j] == "Q"){
                 Console.WriteLine("Left Diag not safe");
                 return false;}
          }

          //check diagonals to the right
          for(int i = row, j = col; i < 4 && j < 4; i++, j++)
          {
              if(board[i, j] == "Q")
                 {Console.WriteLine("Right Diag not safe");
                 return false;}
          }

                    //check diagonals to the left downwards
          for(int i = row, j = col; i < 4 && j >= 0; i++, j--)
          {
              if(board[i, j] == "Q")
                 {Console.WriteLine("Left Diag downwards not safe");
                 return false;}
          }

                    //check diagonals to the right upwards
          for(int i = row, j = col; i >= 0 && j < 4; i--, j++)
          {
              if(board[i, j] == "Q")
                 {Console.WriteLine("Right Diag upwards not safe");
                 return false;}
          }

          //check directly upwards
          for(int i = row; i >= 0; i-- )
          {
              if(board[i, col] == "Q")
                { Console.WriteLine("Upside not safe");

                return false;}
          }

                    //check directly left
          for(int i = col; i >= 0; i-- )
          {
              if(board[row, i] == "Q")
                { Console.WriteLine("Left not safe");

                return false;}
          }
          return true;

        }
        static bool Solve8queen(string[,] board, int col)
        {
            //base case

            if(col >= 4)
            {
                //return true;
                printBoard(board);
                return true;
            }

            //loop over the rows in the current col
             bool res = false;

            for(int i = 0; i < 4; i++)
            {
                if(board[i, col] == "Q"){
                 // i ++;
                  col = 0;

                  Console.WriteLine("row " + i + " col " + col + " is occupied");
                }


                if(checkIfSafe(board, i, col))
                {
                    //place queen
                    board[i, col] = "Q";

                    //explore other solns

                    res = Solve8queen(board, col + 1) || res;

                    //backtrack

                    board[i, col] = ".";
                }
                else
                {
                    //col++;
                }
            }

            return false;
        }


        public static void Main()
        {

           string[,] board = {
                        {".", "Q", ".", "."},
                        {".", ".", ".", "."},
                        {".", ".", ".", "."},
                        {".", ".", ".", "."}

                      };

            //Console.WriteLine(checkIfSafe(board, 0, 1));

            Solve8queen(board, 0);
            //printBoard(board);

            //Console.WriteLine(checkIfSafe(board, 0, 2));
        }
    }
}