QUEENS N PROBLEM

USING THE METHODS GIVEN FINISH THE PROGRAM, I ALREADY DID IT HOWEVER IT ONLY PRINTS ONE SOLUTION AND I WOULD LIKE IT TO PRINT ALL, CAN YOU EDIT MY CODE TO PRINT ALL SOLUTIONS? I WILL COMPARE IT TO MY ORIGINAL CODE TO UNDERSTAND WHAT WAS DONE!

/** * Solves the 8 Queens on an 8x8 chessboard problem. (either 1 or all solutions are fine) * * @author (Potato-San) * @version (1/1/1111) */ import java.util.Scanner; public class Queens { // squares per row or column public static final int BOARD_SIZE = 8;

// used to indicate an empty square public static final int EMPTY = 0;

// used to indicate square contains a queen public static final int QUEEN = 1;

private int board[][]; // chess board

public Queens() { // ------------------------------------------------- // Constructor: Creates an empty square board. // ------------------------------------------------- board = new int[BOARD_SIZE][BOARD_SIZE]; } // end constructor

public void clearBoard() { // ------------------------------------------------- // Clears the board. // Precondition: None. // Postcondition: Sets all squares to EMPTY. // ------------------------------------------------- for(int j = 1; j < 8; j++) { for(int k = 1; k < 8; k++) //Sets every column in this row to 0 { board[j][k] = 0; } //moves on to next row and repeats } } // end clearBoard

public void displayBoard() { // ------------------------------------------------- // Displays the board. // Precondition: None. // Postcondition: Board is written to standard // output; zero is an EMPTY square, one is a square // containing a queen (QUEEN). // ------------------------------------------------- placeQueens(1); int N = board.length; for (int i = 0; i < N; i++) { for (int j = 0; j < N; j++) { if (board[i][j] == 1) { System.out.print("Q "); } else { System.out.print("_|"); } } System.out.println(); } } // end displayBoard

public boolean placeQueens(int column) { // ------------------------------------------------- // Places queens in columns of the board beginning // at the column specified. // Precondition: Queens are placed correctly in // columns 1 through column-1. // Postcondition: If a solution is found, each // column of the board contains one queen and method // returns true; otherwise, returns false (no // solution exists for a queen anywhere in column // specified). // ------------------------------------------------- if (column > BOARD_SIZE) { return true; // base case } else { boolean queenPlaced = false; int row = 1; // number of square in column

while ( !queenPlaced && (row <= BOARD_SIZE) ) { // if square can be attacked if (isUnderAttack(row, column)) { ++row; // consider next square in column } // end if else { // place queen and consider next column setQueen(row, column); queenPlaced = placeQueens(column+1); // if no queen is possible in next column, if (!queenPlaced) { // backtrack: remove queen placed earlier // and try next square in column removeQueen(row, column); ++row; } // end if } // end if } // end while return queenPlaced; } // end if } // end placeQueens

private void setQueen(int row, int column) { // -------------------------------------------------- // Sets a queen at square indicated by row and // column. // Precondition: None. // Postcondition: Sets the square on the board in a // given row and column to QUEEN. // -------------------------------------------------- row = index(row); column = index(column); board[row][column] = 1; //Queen placed on square } // end setQueen

private void removeQueen(int row, int column) { // -------------------------------------------------- // Removes a queen at square indicated by row and // column. // Precondition: None. // Postcondition: Sets the square on the board in a // given row and column to EMPTY. // -------------------------------------------------- column = index(column); for(int x = 0; x < 8 ; x++) { if(board[x][column] == 1) { board[x][column] = 0; x = 8; } }

} // end removeQueen

private boolean isUnderAttack(int row, int column) { // -------------------------------------------------- // Determines whether the square on the board at a // given row and column is under attack by any queens // in the columns 1 through column-1. // Precondition: Each column between 1 and column-1 // has a queen placed in a square at a specific row. // None of these queens can be attacked by any other // queen. // Postcondition: If the designated square is under // attack, returns true; otherwise, returns false. // --------------------------------------------------

//Taking 1-8 & returning 0-7 to suite array row = index(row); column = index(column);

//Checks the rows & columns //Rows for(int i = 0; i < column && i < 8 && row < 8; i++) { //If there's a queen in that row, the queen is under attack if(board[row][i] == 1) { return true; } } //Column

for(int j = 0; j < row && j < 8 && column < 8; j++) { //If there's a queen in that column, the queen is under attack if(board[j][column] == 1) { return true; } }

//Check diagonals for(int i = row, j = column; i >= 0 && j >= 0 && i < 8 && j < 8; i--, j--) { //checks upper diagonal if(board[i][j] == 1) { return true; } }

for(int i = row, j = column; i < board.length && j >= 0 && i < 8 && j < 8; i++, j--) { //checks lower diagonal if(board[i][j] == 1) { return true; } } //At this point the Queen is not being attacked return false; } // end isUnderAttack

private int index(int number) { // -------------------------------------------------- // Returns the array index that corresponds to // a row or column number. // Precondition: 1 <= number <= BOARD_SIZE. // Postcondition: Returns adjusted index value. // -------------------------------------------------- return number - 1; }// end index

public static void main(String[] args) { Queens eight = new Queens(); eight.displayBoard(); } } // end Queens