package algorithm.queen;

public class Queen {
	// 同栏是否有皇后，1表示有
	private int[] column;

	// 右上至左下是否有皇后
	private int[] rup;

	// 左上至右下是否有皇后
	private int[] lup;

	// 解答
	private int[] queen;

	// 解答编号
	private int num;

	public Queen() {
		column = new int[8 + 1];
		rup = new int[2 * 8 + 1];
		lup = new int[2 * 8 + 1];

		for (int i = 1; i <= 8; i++) {
			column[i] = 1;
		}

		for (int i = 1; i <= 2 * 8; i++) {
			rup[i] = lup[i] = 1;
		}

		queen = new int[8 + 1];
	}

	public void backtrack(int i) {
		if (i > 8) {
			showAnswer();
		} else {
			for (int j = 1; j <= 8; j++) {
				if (column[j] == 1 && rup[i + j] == 1 && lup[i - j + 8] == 1) {
					queen[i] = j;
					// 设定为占用
					column[j] = rup[i + j] = lup[i - j + 8] = 0;
					backtrack(i + 1);
					column[j] = rup[i + j] = lup[i - j + 8] = 1;
				}
			}
		}
	}

	protected void showAnswer() {
		num++;
		System.out.println("\n解答" + num);

		for (int y = 1; y <= 8; y++) {
			for (int x = 1; x <= 8; x++) {
				if (queen[y] == x) {
					System.out.print("Q");
				} else {
					System.out.print(".");
				}
			}

			System.out.println();
		}
	}

	public static void main(String[] args) {
		Queen queen = new Queen();
		queen.backtrack(1);
	}
}

package algorithm.queen;

public class Queen {
	// 同栏是否有皇后，1表示有
	private int[] column;

	// 右上至左下是否有皇后
	private int[] rup;

	// 左上至右下是否有皇后
	private int[] lup;

	// 解答
	private int[] queen;

	// 解答编号
	private int num;

	public Queen() {
		column = new int[8 + 1];
		rup = new int[2 * 8 + 1];
		lup = new int[2 * 8 + 1];

		for (int i = 1; i <= 8; i++) {
			column[i] = 1;
		}

		for (int i = 1; i <= 2 * 8; i++) {
			rup[i] = lup[i] = 1;
		}

		queen = new int[8 + 1];
	}

	public void backtrack(int i) {
		if (i > 8) {
			showAnswer();
		} else {
			for (int j = 1; j <= 8; j++) {
				if (column[j] == 1 && rup[i + j] == 1 && lup[i - j + 8] == 1) {
					queen[i] = j;
					// 设定为占用
					column[j] = rup[i + j] = lup[i - j + 8] = 0;
					backtrack(i + 1);
					column[j] = rup[i + j] = lup[i - j + 8] = 1;
				}
			}
		}
	}

	protected void showAnswer() {
		num++;
		System.out.println("\n解答" + num);

		for (int y = 1; y <= 8; y++) {
			for (int x = 1; x <= 8; x++) {
				if (queen[y] == x) {
					System.out.print(" Q ");
				} else {
					System.out.print(" . ");
				}
			}

			System.out.println();
		}
	}

	public static void main(String[] args) {
		Queen queen = new Queen();
		queen.backtrack(1);
	}
}

change queen width