Eight Queens

    import java.io.BufferedReader;
    import java.io.File;
    import java.io.FileReader;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;


    public class Main
    {
            //Directory with sample input data and answers
            private static final String dir = "8queens/data/secret/";

            //chess board
            static int board[][] = new int[8][8];

            //Array lists for input and answer files
            static List<File> inFiles = new ArrayList<File>();
            static List<File> ansFiles = new ArrayList<File>();

            //Initiliazes array lists of files
            public static void initFiles()
            {
                    File folder = new File(dir);

                    for(File f : folder.listFiles())
                    {
                            String ext = f.getName().substring(f.getName().lastIndexOf('.'));
                            //If it's an input file containing board layout
                            if(ext.contains("in"))
                                    inFiles.add(f);
                            //It's an answer file containing the validity of its input
                            else if(ext.contains("ans"))
                                    ansFiles.add(f);
                    }
            }

            public static void main(String[] args) throws IOException
            {
                    initFiles();
                    for(int x = 0; x < inFiles.size(); x++)
                    {
                            //next file
                            File input = inFiles.get(x);

                            FileReader fr = new FileReader(input);
                            BufferedReader br = new BufferedReader(fr);

                            //Iterate over matrix, input file data
                            for(int i = 0; i < 8; i++)
                            {
                                    //Read first line
                                    String line = br.readLine();
                                    for(int j = 0; j < 8; j++)
                                    {
                                            //next char in line
                                            char c = line.charAt(j);
                                            //asterisks are queens, therefore 1's
                                            if(c == '*')
                                                    board[i][j] = 1;
                                            //no queen means a 0
                                            else
                                                    board[i][j] = 0;
                                    }
                            }

                            fr.close();
                            br.close();

                            //to assist breaking out of nested loop
                            boolean keepGoing = true;

                            for(int i = 0; i < 8; i++)
                            {
                                    for(int j = 0; j < 8; j++)
                                    {
                                            //if we find a queen
                                            if(board[i][j] == 1)
                                            {
                                                    //check if it is placed well
                                                    if(!validChoice(i, j))
                                                    {
                                                            //if not, algorithm can stop
                                                            keepGoing = false;
                                                            break;
                                                    }
                                            }
                                    }
                                    if(!keepGoing)
                                            break;
                            }

                            String myAnswer = null;

                            if(keepGoing)
                                    myAnswer = "valid";
                            else
                                    myAnswer = "invalid";

                            File ans = ansFiles.get(x);

                            fr = new FileReader(ans);
                            br = new BufferedReader(fr);

                            //get judges answer
                            String answer = br.readLine();

                            fr.close();
                            br.close();

                            //if our answers dont match, let me know which file
                            if(!answer.contains(myAnswer))
                                    System.out.println(ans.getName());
                            else
                                    System.out.println(myAnswer);
                    }

            }

            private static boolean validChoice(int row, int column)
            {
                    if(row > 7 || column > 7)
                            return false;

                    int rowSum = 0;
                    int columnSum = 0;
                    int diagnolSum1 = 0;
                    int diagnolSum2 = 0;

                    for(int i = 0; i < 8; i++)
                    {
                            //how many queens in the row?
                            //should be 1 to be valid
                            rowSum += board[row][i];
                            //how many queens in column?
                            //should b 1 to be valid;
                            columnSum += board[i][column];
                    }

                    //down and right diagnol
                    int currCol = column;
                    for(int i = row + 1; i < 8; i++)
                    {
                            currCol++;
                            if(currCol > 7)
                                    break;
                            diagnolSum2 += board[i][currCol];
                    }

                    //up and left diagnol
                    currCol = column;
                    for(int i = row - 1; i >= 0; i--)
                    {
                            currCol--;
                            if(currCol < 0)
                                    break;
                            diagnolSum2 += board[i][currCol];
                    }

                    //down and left diagnol
                    currCol = column;
                    for(int i = row + 1; i < 8; i++)
                    {
                            currCol--;
                            if(currCol < 0)
                                    break;
                            diagnolSum1 += board[i][currCol];
                    }

                    //up and right diagnol
                    currCol = column;
                    for(int i = row - 1; i >= 0; i--)
                    {
                            currCol++;
                            if(currCol > 7)
                                    break;
                            diagnolSum1 += board[i][currCol];
                    }

                    if(rowSum <= 1 && columnSum <= 1 && diagnolSum1 < 1 && diagnolSum2 < 1)
                            return true;

                    return false;
            }
    }