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  1. public class Main {
  2. //Number of rows or columns
  3. public static final int BOARD_SIZE = 8;
  4.  
  5. boolean[][] board;
  6. //Indicate an empty square
  7. public static final boolean EMPTY = false;
  8. //Indicate a square which containing a queen
  9. public static final boolean QUEEN = true;
  10. //Number of moves
  11. public static final int MOVES = 4;
  12. //Horizontal moves
  13. int[] horizontal;
  14. //Vertical moves
  15. int[] vertical;
  16.  
  17. public int queens = 0;
  18.  
  19. public static void main(String[] s) {
  20.     Main main = new Main();
  21.     main.placeQueens(0);
  22.     main.displayBoard();
  23. }
  24. public Main() {
  25.     //Constructor creates an empty board
  26.     board = new boolean[BOARD_SIZE][BOARD_SIZE];
  27.     for (int row = 0; row < board.length; row++) {
  28.         for (int col = 0; col < board[row].length; col++) {
  29.             board[row][col] = EMPTY;
  30.         }
  31.     }
  32.  
  33.     horizontal = new int[MOVES];
  34.     vertical = new int[MOVES];
  35.     // up right
  36.     horizontal[0] = -1;
  37.     vertical[0] = 1; 
  38.     // down left
  39.     horizontal[1] = 1;
  40.     vertical[1] = -1;
  41.     // up left
  42.     horizontal[2] = -1;
  43.     vertical[2] = -1;
  44.     // down right
  45.     horizontal[3] = 1;
  46.     vertical[3] = 1;
  47.  
  48.  
  49. }
  50.  
  51. public boolean placeQueens (int column) {
  52.  
  53.     if (column >= BOARD_SIZE) {
  54.         return true;
  55.     }
  56.     else {
  57.         boolean queenPlaced = false;
  58.         int row = 0;
  59.  
  60.         while (!queenPlaced && row < BOARD_SIZE) {
  61.             if (isUnderAttack(row, column)) {
  62.                 ++row;
  63.             }// end if
  64.             else{
  65.                 setQueen(row, column);
  66.                 queenPlaced = placeQueens(column + 1);
  67.                 if (!queenPlaced) {
  68.                     removeQueen(row,column);
  69.                     ++row;
  70.                 }// end if
  71.             }// end else
  72.         }// end while
  73.         return queenPlaced;
  74.     }// end else
  75. }
  76.  
  77.  
  78. private void removeQueen(int row, int column) {
  79.     board[row][column] = EMPTY;
  80.     System.out.printf("queen REMOVED from [%d][%d]\n", row, column);
  81. --queens;
  82. }
  83.  
  84. private void setQueen(int row, int column) {
  85.     board[row][column] = QUEEN;
  86.     System.out.printf("queen PLACED in [%d][%d]\n", row, column);
  87.     ++queens;
  88.  
  89. }
  90.  
  91. public boolean isUnderAttack(int row, int col) {
  92.  
  93.     boolean condition = false;
  94.     // check row
  95.     for (int column = 0; column < BOARD_SIZE; column++) {
  96.         if ((board[row][column] == true)) {
  97.             condition = true;
  98.         }
  99.     }
  100.  
  101.     // check column
  102.     for (int row_ = 0; row_ < board.length; row_++) {
  103.         if (board[row_][col] == true) {
  104.                     condition = true;
  105.         }
  106.     }
  107.  
  108.     // check diagonal
  109.     for (int row_ = row, col_ = col; row_ >= 0 && col_ < 8; row_ += horizontal[0], col_ += vertical[0]) {
  110.         if (board[row_][col_] == true) {
  111.             condition = true;
  112.         }
  113.     }
  114.     for (int row_ = row, col_ = col; row_ < 8 && col_ >= 0; row_ += horizontal[1], col_ += vertical[1]) {
  115.         if (board[row_][col_] == true) {
  116.             condition = true;
  117.         }
  118.     }
  119.     for (int row_ = row, col_ = col; row_ >= 0 && col_ >= 0; row_ += horizontal[2], col_ += vertical[2]) {
  120.         if (board[row_][col_] == true) {
  121.             condition = true;
  122.         }
  123.     }
  124.     for (int row_ = row, col_ = col; row_ < 8 && col_ < 8; row_ += horizontal[3], col_ += vertical[3]) {
  125.         if (board[row_][col_] == true) {
  126.             condition = true;
  127.         }
  128.     }
  129.  
  130.     return condition;
  131. }
  132.  
  133. public void displayBoard () {
  134.     int counter = 0;
  135.     for (int row = 0; row < board.length; row++) {
  136.         for (int col = 0; col < board[row].length; col++) {
  137.             if (board[row][col] == true) {
  138.                 System.out.printf("|%s|", "x");
  139.                 counter++;
  140.             }
  141.             else {              
  142.                 System.out.printf("|%s|", "o");
  143.             }
  144.         }
  145.         System.out.println();
  146.  
  147.     }
  148.  
  149.     System.out.printf("%d queens has been placed\n", counter);
  150. }
  151. }
  152.  
  153.  
Success #stdin #stdout 0.09s 245888KB
comments (?)
stdin
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Standard input is empty
stdout
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queen PLACED in [0][0]
queen PLACED in [2][1]
queen PLACED in [4][2]
queen PLACED in [1][3]
queen PLACED in [3][4]
queen REMOVED from [3][4]
queen PLACED in [7][4]
queen REMOVED from [7][4]
queen REMOVED from [1][3]
queen PLACED in [6][3]
queen PLACED in [1][4]
queen PLACED in [3][5]
queen PLACED in [5][6]
queen REMOVED from [5][6]
queen REMOVED from [3][5]
queen REMOVED from [1][4]
queen PLACED in [3][4]
queen REMOVED from [3][4]
queen REMOVED from [6][3]
queen PLACED in [7][3]
queen PLACED in [1][4]
queen PLACED in [3][5]
queen PLACED in [5][6]
queen REMOVED from [5][6]
queen REMOVED from [3][5]
queen REMOVED from [1][4]
queen PLACED in [3][4]
queen REMOVED from [3][4]
queen REMOVED from [7][3]
queen REMOVED from [4][2]
queen PLACED in [5][2]
queen PLACED in [1][3]
queen PLACED in [6][4]
queen PLACED in [4][5]
queen REMOVED from [4][5]
queen REMOVED from [6][4]
queen REMOVED from [1][3]
queen PLACED in [7][3]
queen PLACED in [1][4]
queen PLACED in [3][5]
queen REMOVED from [3][5]
queen PLACED in [4][5]
queen REMOVED from [4][5]
queen REMOVED from [1][4]
queen REMOVED from [7][3]
queen REMOVED from [5][2]
queen PLACED in [6][2]
queen PLACED in [1][3]
queen PLACED in [3][4]
queen PLACED in [7][5]
queen REMOVED from [7][5]
queen REMOVED from [3][4]
queen PLACED in [7][4]
queen PLACED in [4][5]
queen REMOVED from [4][5]
queen REMOVED from [7][4]
queen REMOVED from [1][3]
queen REMOVED from [6][2]
queen PLACED in [7][2]
queen PLACED in [1][3]
queen PLACED in [3][4]
queen REMOVED from [3][4]
queen PLACED in [6][4]
queen REMOVED from [6][4]
queen REMOVED from [1][3]
queen PLACED in [5][3]
queen PLACED in [1][4]
queen REMOVED from [1][4]
queen PLACED in [3][4]
queen PLACED in [1][5]
queen PLACED in [4][6]
queen REMOVED from [4][6]
queen REMOVED from [1][5]
queen REMOVED from [3][4]
queen REMOVED from [5][3]
queen REMOVED from [7][2]
queen REMOVED from [2][1]
queen PLACED in [3][1]
queen PLACED in [1][2]
queen PLACED in [4][3]
queen PLACED in [2][4]
queen REMOVED from [2][4]
queen PLACED in [7][4]
queen REMOVED from [7][4]
queen REMOVED from [4][3]
queen PLACED in [6][3]
queen PLACED in [2][4]
queen REMOVED from [2][4]
queen REMOVED from [6][3]
queen PLACED in [7][3]
queen PLACED in [2][4]
queen PLACED in [6][5]
queen REMOVED from [6][5]
queen REMOVED from [2][4]
queen PLACED in [5][4]
queen PLACED in [2][5]
queen REMOVED from [2][5]
queen REMOVED from [5][4]
queen REMOVED from [7][3]
queen REMOVED from [1][2]
queen PLACED in [5][2]
queen PLACED in [2][3]
queen REMOVED from [2][3]
queen PLACED in [7][3]
queen PLACED in [1][4]
queen PLACED in [4][5]
queen PLACED in [2][6]
queen REMOVED from [2][6]
queen REMOVED from [4][5]
queen PLACED in [6][5]
queen PLACED in [2][6]
queen REMOVED from [2][6]
queen REMOVED from [6][5]
queen REMOVED from [1][4]
queen PLACED in [2][4]
queen PLACED in [4][5]
queen REMOVED from [4][5]
queen PLACED in [6][5]
queen REMOVED from [6][5]
queen REMOVED from [2][4]
queen REMOVED from [7][3]
queen REMOVED from [5][2]
queen PLACED in [6][2]
queen PLACED in [2][3]
queen PLACED in [5][4]
queen PLACED in [1][5]
queen PLACED in [4][6]
queen REMOVED from [4][6]
queen REMOVED from [1][5]
queen REMOVED from [5][4]
queen PLACED in [7][4]
queen PLACED in [1][5]
queen PLACED in [4][6]
queen REMOVED from [4][6]
queen REMOVED from [1][5]
queen REMOVED from [7][4]
queen REMOVED from [2][3]
queen PLACED in [4][3]
queen PLACED in [1][4]
queen REMOVED from [1][4]
queen PLACED in [2][4]
queen REMOVED from [2][4]
queen PLACED in [7][4]
queen PLACED in [1][5]
queen REMOVED from [1][5]
queen REMOVED from [7][4]
queen REMOVED from [4][3]
queen REMOVED from [6][2]
queen PLACED in [7][2]
queen PLACED in [2][3]
queen REMOVED from [2][3]
queen PLACED in [4][3]
queen PLACED in [1][4]
queen REMOVED from [1][4]
queen PLACED in [2][4]
queen REMOVED from [2][4]
queen REMOVED from [4][3]
queen REMOVED from [7][2]
queen REMOVED from [3][1]
queen PLACED in [4][1]
queen PLACED in [1][2]
queen PLACED in [5][3]
queen PLACED in [2][4]
queen PLACED in [6][5]
queen PLACED in [3][6]
queen REMOVED from [3][6]
queen REMOVED from [6][5]
queen REMOVED from [2][4]
queen REMOVED from [5][3]
queen PLACED in [7][3]
queen PLACED in [2][4]
queen PLACED in [6][5]
queen PLACED in [3][6]
queen REMOVED from [3][6]
queen REMOVED from [6][5]
queen REMOVED from [2][4]
queen PLACED in [5][4]
queen PLACED in [2][5]
queen REMOVED from [2][5]
queen PLACED in [3][5]
queen REMOVED from [3][5]
queen REMOVED from [5][4]
queen REMOVED from [7][3]
queen REMOVED from [1][2]
queen PLACED in [6][2]
queen PLACED in [1][3]
queen PLACED in [3][4]
queen PLACED in [7][5]
queen REMOVED from [7][5]
queen REMOVED from [3][4]
queen PLACED in [5][4]
queen PLACED in [2][5]
queen REMOVED from [2][5]
queen PLACED in [7][5]
queen REMOVED from [7][5]
queen REMOVED from [5][4]
queen REMOVED from [1][3]
queen REMOVED from [6][2]
queen PLACED in [7][2]
queen PLACED in [1][3]
queen PLACED in [3][4]
queen PLACED in [6][5]
queen PLACED in [2][6]
queen REMOVED from [2][6]
queen REMOVED from [6][5]
queen REMOVED from [3][4]
queen PLACED in [6][4]
queen PLACED in [2][5]
queen PLACED in [5][6]
queen REMOVED from [5][6]
queen REMOVED from [2][5]
queen REMOVED from [6][4]
queen REMOVED from [1][3]
queen PLACED in [5][3]
queen PLACED in [2][4]
queen PLACED in [6][5]
queen PLACED in [1][6]
queen PLACED in [3][7]
|x||o||o||o||o||o||o||o|
|o||o||o||o||o||o||x||o|
|o||o||o||o||x||o||o||o|
|o||o||o||o||o||o||o||x|
|o||x||o||o||o||o||o||o|
|o||o||o||x||o||o||o||o|
|o||o||o||o||o||x||o||o|
|o||o||x||o||o||o||o||o|
8 queens has been placed
https://ideone.com/8iamUa
language:
Java (HotSpot 12)
created:
12 years ago
visibility:
secret

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