第一次试验---八皇后问题和聚类思考

public class Queen_Java {
 int QUEEN_COUNT = 4; // 是多少皇后
 static final int EMPTY = 0;
 int[][] count = new int[QUEEN_COUNT][QUEEN_COUNT];
 int[] QueenIndex = new int[QUEEN_COUNT];
 int resultCount = 0;
 long time = System.currentTimeMillis();

 public void putQueenIndex(int row) {
  for (int col = 0; col < QUEEN_COUNT; col++) {
   if (count[row][col] == EMPTY) {
    for (int iRow = row + 1; iRow < QUEEN_COUNT; iRow++) {
     count[iRow][col]++;
     if ((col - iRow + row) >= 0) {
      count[iRow][col - iRow + row]++;
     }
     if ((col + iRow - row) < QUEEN_COUNT) {
      count[iRow][col + iRow - row]++;
     }
    }
    QueenIndex[row] = col;
    if (row == QUEEN_COUNT - 1) {
     print(++resultCount);
    } else {
     putQueenIndex(row + 1);
    }
    for (int iRow = row + 1; iRow < QUEEN_COUNT; iRow++) {
     count[iRow][col]--;
     if ((col - iRow + row) >= 0) {
      count[iRow][col - iRow + row]--;
     }
     if ((col + iRow - row) < QUEEN_COUNT) {
      count[iRow][col + iRow - row]--;
     }
    }
   }
  }
  if (row == 0) {
   System.out.println(QUEEN_COUNT + "皇后共有 " + resultCount + " 个解\n"
     + (System.currentTimeMillis() - time) + "毫秒");
  }
 }

 public void print(int n) {
  System.out.println(QUEEN_COUNT + "皇后的第 " + n + " 个解：");
  for (int i = 0; i < QUEEN_COUNT; i++) {
   for (int j = 0; j < QUEEN_COUNT; j++) {
    System.out.print(QueenIndex[i] == j ? "Q" : "X");
   }
   System.out.println();
  }
  System.out.println();
 }

 public static void main(String[] args) {
  new Queen_Java().putQueenIndex(0);
 }
}