EightQueensProblem.java

package miscellaneous;

public class EightQueensProblem {

    public static char[][] finalBoard;

    private EightQueensProblem() {

    }

    public static boolean doesHaveEightQueensProblemSolution(int nth) {
        char[][] board = new char[nth][nth];
        for (int i = 0; i < nth; i++)
            for (int j = 0; j < nth; j++)
                board[i][j] = '-';
        if (solveNQueens(board, 0, nth)) {
            solution(board, nth);
            finalBoard = board;
            return true;
        } else {
            System.out.println("No solution exists");
            finalBoard = new char[nth][nth];
            return false;
        }
    }

    public static void solution(char[][] board, int n) {
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++)
                System.out.print(" " + board[i][j] + " ");
            System.out.println();
        }
    }

    public static boolean isSafe(char[][] board, int row, int column, int n) {
        int i, j;
        for (i = 0; i < column; i++) {
            if (board[row][i] == 'Q') return false;
        }
        for (i = row, j = column; i >= 0 && j >= 0; i--, j--) {
            if (board[i][j] == 'Q') return false;
        }
        for (i = row, j = column; i < n && j >= 0; i++, j--) {
            if (board[i][j] == 'Q') return false;
        }
        return true;
    }

    public static boolean solveNQueens(char[][] board, int column, int n) {
        if (column >= n) return true;
        for (int i = 0; i < n; i++) {
            if (isSafe(board, i, column, n)) {
                board[i][column] = 'Q';
                if (solveNQueens(board, column + 1, n)) return true;
                board[i][column] = '-';
            }
        }
        return false;
    }
}