Poj2676

经典DFS现在看来nice啊！

package SoduKu;

import java.io.InputStreamReader;
import java.util.Scanner;
/*
 *我用row[k][i]表示第k行是否已经有数i
 *col[k][i]表示第k列是否已经有数i
 *而sq[k][i]表示第k个九宫格是否有数i（这里k=(x/3)*3+(y/3),可以想想为什么）
 *从0,0 依次搜到8,8  DFS依次往下
 **/
public class Poj2676{

    static int[][] map = new int[9][9];
    static int[][] col = new int[9][9];
    static int[][] row = new int[9][9];
    static int[][] sq  = new int[9][9];
    static boolean isFind = false;
    static void fill(int[][] a){
        for(int i = 0; i < 9; ++i){
            for(int j = 0; j < 9; ++j)
                a[i][j] = 0;
        }
    }
    static void print(){
        for(int i = 0; i < 9; ++i) {
            for(int j = 0; j < 9; ++j){
                System.out.print(map[i][j]+1);
            }
            System.out.println();
        }
    }

    static void dfs(int x, int y){
        int u = x*9 + y + 1;
        if(x == 9){
            isFind = true;
            print();
        }

        if(isFind)
            return;
        if(map[x][y] != -1){
            dfs(u/9, u%9);
            return;
        }

        for(int i = 0; i < 9 && !isFind; ++i){
            int k = (x/3)*3 + y/3;
            if(row[x][i] == 0 && col[y][i] == 0 && sq[k][i] == 0){
                row[x][i] = col[y][i] = sq[k][i] = 1;
                map[x][y] = i;

                dfs(u/9, u%9);

                row[x][i] = col[y][i] = sq[k][i] = 0;
                map[x][y] = -1;
            }
        }
    }
    public static void main(String[] args){
        Scanner scanner = new Scanner(new InputStreamReader(System.in));

        int k;
        int n = scanner.nextInt();
        scanner.nextLine();
        for(int ni = 1; ni <= n; ++ni){

            fill(map);
            fill(row);
            fill(col);
            fill(sq);
            isFind = false;
            for(int i = 0; i < 9; ++i){
                String string = scanner.nextLine();
                for(int j = 0; j < 9; ++j) {
                    k = string.charAt(j) - '0';
                    map[i][j] = k-1;
                    if(k != 0){
                        row[i][k-1] = col[j][k-1] = sq[(i/3)*3 + (j/3)][k-1] = 1;
                    }
                }
            }
            dfs(0, 0);
        }
    }
}