数独问题—题解

标签：数独   数独问题   

CPU消耗  < 2000ms

import java.util.Scanner;

/**
 * 
 *
 *   数独游戏
 *   
 测试数据1：
0 0 5 3 0 0 0 0 0
8 0 0 0 0 0 0 2 0
0 7 0 0 1 0 5 0 0
4 0 0 0 0 5 3 0 0
0 1 0 0 7 0 0 0 6
0 0 3 2 0 0 0 8 0
0 6 0 5 0 0 0 0 9
0 0 4 0 0 0 0 3 0
0 0 0 0 0 9 7 0 0
测试数据2：
8 0 0 0 0 0 0 0 0
0 0 3 6 0 0 0 0 0
0 7 0 0 9 0 2 0 0
0 5 0 0 0 7 0 0 0
0 0 0 0 4 5 7 0 0
0 0 0 1 0 0 0 3 0
0 0 1 0 0 0 0 6 8
0 0 8 5 0 0 0 1 0
0 9 0 0 0 0 4 0 0

 *
 */

public class Main
{
	public static boolean flag = false;   // 标记是否已找到
	
    public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);
        int arr[][] = new int [10][10];
        for (int i = 1; i < arr.length; i++)
        for (int j = 1; j < arr[i].length; j++)
             arr[i][j] = sc.nextInt();
        sc.close();
        
        dfs(1, 1, arr);
	}

	private static void dfs(int x, int y, int[][] arr)
	{
		if (flag)  return ;
		
		if (x > 9) 
		{
			output(arr); flag = true;
			return ;
		}
	    if (y > 9)
	    {
	    	dfs(x+1, 1, arr); 
	    }
	    else if (arr[x][y] != 0) dfs(x,y+1,arr);
	    else
	    {
	    	for (int i = 1; i < 10; i++)
	    	{
	    		if (check(x, y, i, arr))
	    		{
	    			arr[x][y] = i;
	    			dfs(x, y+1, arr);
	    			arr[x][y] = 0;
	    		}
	    	}
	    }
	}
    
	private static boolean check(int x, int y, int num, int[][] arr)
	{
		// 检查x轴
		for (int i = 1; i < 10; i++)
		{
			if (arr[x][i] == num) return false;
		}
		// 检查y轴
		for (int i = 1; i < 10; i++)
		{
			if (arr[i][y] == num) return false;
		}
		// 检查九宫格
         for (int i = (x-1)/3*3+1; i <= (x-1)/3*3+3; i++)
         {
        	 for (int j = (y-1)/3*3+1; j <= (y-1)/3*3+3; j++)
        	 {
        		 if (arr[i][j] == num) return false;
        	 }
         }
		return true;
	}

	private static void output(int[][] arr)
	{
		 for (int i = 1; i < arr.length; i++)
		 {
			 for (int j = 1; j < arr[i].length; j++)
			 {
				System.out.print(arr[i][j] + " "); 
			 }
			 System.out.println();
		 }
	}
}

数独问题—题解

标签：数独   数独问题   

原文地址：http://blog.csdn.net/first_sight/article/details/44131635