N-Queen

Day 35: 9663 (https://www.acmicpc.net/problem/9663)

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static boolean checkThreat(boolean[][] currentBoard, int xToCheck, int yToCheck)
{
    for (Tuple<Integer> t: queensOnBoard)
    {
        if (onDiagonal(t, xToCheck, yToCheck) || onHoriVerti(t, xToCheck, yToCheck)) {
            return true;
        }
    }
    return false;
}
 
static boolean onDiagonal(Tuple queenOnBoard, int xToCheck, int yToCheck)
{
    int xDiff = queenOnBoard.x - xToCheck;
    int yDiff = queenOnBoard.y - yToCheck;
    
    if (xDiff == 0) {
        return false;
    } else {
        return Math.abs(yDiff/xDiff) == 1.0;
    }
}
 
static boolean onHoriVerti(Tuple queenOnBoard, int xToCheck, int yToCheck)
{
    int queenX = queenOnBoard.x;
    int queenY = queenOnBoard.y;
    
    return queenX == xToCheck || queenY == yToCheck;
}

static class Tuple<Integer>
{
    public int x;
    public int y;
 
    public Tuple(int x, int y)
    {
        this.x = x;
        this.y = y;
    }
}

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
 
public class b9663
{
    static int N;
    static int numWays;
    static ArrayList<Tuple> queensOnBoard;
    
    
    static boolean addQueen(boolean[][] currentBoard, int xToAdd, int yToAdd)
    {
        if (!checkThreat(currentBoard, xToAdd, yToAdd)) {
            currentBoard[xToAdd][yToAdd] = true;
            return queensOnBoard.add(new Tuple(xToAdd, yToAdd));
        }
        return false;
    }
    
    static void simulateQueens(boolean[][] board, ArrayList<Tuple> queensOnBoard, int startingX, int startingY)
    {
        for (int k = 0; k < N; k++)
        {
            int rowsCompleted = 0;
            
            for (int rowIndex = 0; rowIndex < N; rowIndex++)
            {
                for (int columnIndex = 0; columnIndex < N; columnIndex++)
                {
                    if (addQueen(board, rowIndex, columnIndex)) {
                        rowsCompleted++;
                        break;
                        
                    } else if (columnIndex == N-1){
                        
                    }
                }
            }
            
            if (rowsCompleted == N) numWays++;
            debugCase(board, N);
        }
    }
    
    public static void main(String[] args) throws Exception
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        N = Integer.parseInt(br.readLine());
        boolean[][] board = new boolean[N][N];
        queensOnBoard = new ArrayList<Tuple>();
        
        simulateQueens(board, queensOnBoard, 0, 0);
    }
    
    
    static void debugCase(boolean[][] board, int N)
    {
        System.out.println(numWays);
 
        for (int i = 0; i < N; i++)
        {
            for (int j = 0; j < N; j++)
            {
                if (board[i][j]) System.out.print(1 + " ");
                else System.out.print(0 + " ");
            }
            System.out.println();
        }
    }
}

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