8格骑士巡游的不完全回溯法

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import java.util.Scanner;

public class KnightSeemsRight {

	public static final int MAX_EXITS = 8;

	public static final int SIDE_LENGTH = 8;

	static int[][] board = new int[SIDE_LENGTH][SIDE_LENGTH];

	static int[] nexti = new int[MAX_EXITS];

	static int[] nextj = new int[MAX_EXITS];

	static int npos;

	static int kti, ktj;

	static int[] ktmove1 = { -2, -1, 1, 2, 2, 1, -1, -2 };

	static int[] ktmove2 = { 1, 2, 2, 1, -1, -2, -2, -1 };

	static int[] exits = new int[MAX_EXITS];

	public static void main(String args[]) {
	 
		Scanner input = new Scanner(System.in);
		System.out.printf("骑士巡游问题\n");

		boolean flag=false;
		while(true)
		{
		while (true) {
			System.out.printf("输入骑士的开始位置:\n");

			

			kti = input.nextInt();
			ktj = input.nextInt();
			kti--;
			ktj--;
			// 从0开始，所以只到7而已
			if (!((kti >= 0) && (kti < MAX_EXITS)) || // 超出边界出错
					!((ktj >= 0) && (ktj < MAX_EXITS))) {
				System.out.printf("输入错误\n");
				continue;
			}
			break;
		}
		knight_tour();
	

	}
		
		 
	}

	public static void knight_tour() {
		int i, j, k, l, m, min;
		int starti, startj;

		for (i = 0; i < SIDE_LENGTH; i++)
			for (j = 0; j < SIDE_LENGTH; j++)
				board[i][j] = 0;
		
		
		board[kti][ktj] = 1;
		starti = kti;
		startj = ktj;
		for (m = 1; m <= 63; m++) {
			npos = 0;
			for (k = 0; k < MAX_EXITS; k++) { // 试各个方向
				i = kti + ktmove1[k];
				j = ktj + ktmove2[k];
				if (i >= 0 && i < MAX_EXITS && j >= 0 && j < MAX_EXITS
						&& board[i][j]==0) { // 可行
					nexti[npos] = i;
					nextj[npos] = j;
					npos++;
				}
			}
			if (npos == 0) {
				System.out.printf("Knight tour failed at m = %d.\n", m);
				break;
			} else if (npos == 1)
				min = 0;
			else {
				for (l = 0; l < npos; l++)
					exits[l] = 0;
				min = 0;
				for (l = 0; l < npos; l++) {
					for (k = 0; k < MAX_EXITS; k++) {
						i = nexti[l] + ktmove1[k];
						j = nextj[l] + ktmove2[k];
						if (i >= 0 && i < MAX_EXITS && j >= 0 && j < MAX_EXITS
								&& board[i][j]==0) {
							exits[l]++;
						}
					}
					if (exits[l] < exits[min])
						min = l;
				}
			}
			kti = nexti[min];
			ktj = nextj[min];
			board[kti][ktj] = m;
		}
		
		//输出
		for (i = 0; i < SIDE_LENGTH; i++) {
			for (j = 0; j < SIDE_LENGTH; j++)
				if (i == starti && j == startj)
					System.out.printf("%4s", "K");
				else
					System.out.printf("%4d", board[i][j]);
			System.out.printf("\n");
		}
//		输出
	}

}