Vorlesung 5 / Aufgabe 2

VL05/Aufgabe02/Aufgabe02.java

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+package VL05.Aufgabe02;
+
+/**
+ * Vorlesung 5 / Aufgabe 2
+ *
+ * @author Sebastian Brosch
+ */
+public class Aufgabe02 {
+  public static void main(String[] args) {
+    final int DAMEN = 8;
+    int chessboard[][] = new int[DAMEN][DAMEN];
+    queens(chessboard, 1);
+  }
+
+  /**
+   * Method to place a queen on the chessboard.
+   *
+   * @param chessboard The chessboard to place the queen.
+   * @param q          The number of the queen to be placed.
+   */
+  private static void queens(int[][] chessboard, int q) {
+    if (q > chessboard.length) {
+      print(chessboard);
+      return;
+    } else {
+      for (int i = 0; i < chessboard.length; i++) {
+        if (isQueenPossible(chessboard, q - 1, i)) {
+
+          chessboard[q - 1][i] = 1;
+          queens(chessboard, q + 1);
+          chessboard[q - 1][i] = 0;
+        }
+      }
+    }
+  }
+
+  /**
+   * Method to check whether a queen can be placed on the field.
+   *
+   * @param chessboard The chessboard to place the queen.
+   * @param row        The row to place the queen.
+   * @param column     The column to place the queen.
+   * @return The state whether the queen can be placed on the field.
+   */
+  private static boolean isQueenPossible(int[][] chessboard, int row, int column) {
+    int currentRow = 0;
+    int currentColumn = 0;
+
+    // check whether the queen can be placed in current row.
+    for (int c = 0; c < chessboard[row].length; c++) {
+      if (chessboard[row][c] == 1)
+        return false;
+    }
+
+    // check whether the queen can be placed in current column.
+    for (int r = 0; r < chessboard.length; r++) {
+      if (chessboard[r][column] == 1)
+        return false;
+    }
+
+    // check whether the queen can be placed diagonal (top left).
+    currentRow = row;
+    currentColumn = column;
+
+    while (currentColumn >= 0 && currentRow >= 0) {
+      if (chessboard[currentRow][currentColumn] == 1)
+        return false;
+
+      currentRow--;
+      currentColumn--;
+    }
+
+    // check whether the queen can be placed diagonal (bottom right).
+    currentRow = row;
+    currentColumn = column;
+
+    while (currentColumn < chessboard[row].length && currentRow < chessboard.length) {
+      if (chessboard[currentRow][currentColumn] == 1)
+        return false;
+
+      currentRow++;
+      currentColumn++;
+    }
+
+    // check whether the queen can be placed diagonal (bottom left).
+    currentRow = row;
+    currentColumn = column;
+
+    while (currentColumn >= 0 && currentRow < chessboard.length) {
+      if (chessboard[currentRow][currentColumn] == 1)
+        return false;
+
+      currentRow++;
+      currentColumn--;
+    }
+
+    // check whether the queen can be placed diagonal (top right).
+    currentRow = row;
+    currentColumn = column;
+
+    while (currentColumn < chessboard[row].length && currentRow >= 0) {
+      if (chessboard[currentRow][currentColumn] == 1)
+        return false;
+
+      currentRow--;
+      currentColumn++;
+    }
+
+    return true;
+  }
+
+  /**
+   * Method to print a chessboard.
+   *
+   * @param chessboard The chessboard to be printed.
+   */
+  private static void print(int[][] chessboard) {
+    System.out.println("\nChessboard:\n");
+
+    for (int r = 0; r < chessboard.length; r++) {
+      for (int c = 0; c < chessboard[r].length; c++) {
+        System.out.printf("%d", chessboard[r][c]);
+      }
+
+      System.out.printf("\n");
+    }
+  }
+}