编辑代码

public class EightQueens {  
    private static final int SIZE = 8;  
    private int[] solution = new int[SIZE];  
    private int count = 0;  
  
    public static void main(String[] args) {  
        EightQueens eightQueens = new EightQueens();  
        eightQueens.placeQueen(0);  
        System.out.println("共有 " + eightQueens.count + " 种解法");  
    }  
  
    private void placeQueen(int row) {  
        for (int i = 0; i < SIZE; i++) {  
            if (isValid(row, i)) {  
                solution[row] = i;  
                if (row == SIZE - 1) {  
                    printSolution();  
                    count++;  
                } else {  
                    placeQueen(row + 1);  
                }  
            }  
        }  
    }  
  
    private boolean isValid(int row, int col) {  
        for (int i = 0; i < row; i++) {  
            if (solution[i] == col || Math.abs(solution[i] - col) == Math.abs(i - row)) {  
                return false;  
            }  
        }  
        return true;  
    }  
  
    private void printSolution() {  
        for (int i = 0; i < SIZE; i++) {  
            for (int j = 0; j < SIZE; j++) {  
                if (solution[i] == j) {  
                    System.out.print("Q ");  
                } else {  
                    System.out.print(". ");  
                }  
            }  
            System.out.println();  
        }  
        System.out.println();  
    }  
}