Sudoku(dfs)

http://poj.org/problem?id=2676

填九宫格

思路：将每一行，每一列及每一个3*3块中出现的数字标记上，将可填的空的位置记录下来，枚举1-9，填入合适的数。

#include <stdio.h>
#include <string.h>
int row[10][10],col[10][10],arr[10][10];//row[x][i]表示i所在的行为x;
                                        //col[y][i]表示i所在的列为y;
                                        //arr[n][i]表示i所在的3*3方格;
int keep[82][2],map[10][10],num,t;      //keep[][]记录可填数的位置;
void show()
{
    for (int i = 0;i < 9;i ++)
    {
        for (int j = 0;j < 9;j ++)
        {
            printf("%d",map[i][j]);
        }
        puts("");
    }
}
int dfs(int x,int y)
{
    if (t==num)
    {
        show();
        return 1;
    }
    for (int i = 1;i <= 9;i ++)
    {
        int k = x/3*3+y/3;
        if (!row[x][i]&&!col[y][i]&&!arr[k][i])
        {
            map[x][y] = i;
            row[x][i] = 1;
            col[y][i] = 1;
            arr[k][i] = 1;
            ++t;
            if (dfs(keep[t][0],keep[t][1]))
            return 1;
            --t; 
            //回溯过程中，清除标记
            map[x][y] = 0;
            row[x][i] = 0;
            col[y][i] = 0;
            arr[k][i] = 0;

        }
    }
    return 0;

}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
         t = 0;
         memset(row,0,sizeof(row));
         memset(col,0,sizeof(col));
         memset(arr,0,sizeof(arr));
         memset(keep,0,sizeof(keep));
        for (int i = 0;i < 9;i ++)
        {
            for (int j = 0;j < 9;j ++)
            {
                scanf("%1d",&map[i][j]);//控制格式输入
                if (map[i][j])
                {
                    int k = i/3*3+j/3;
                    row[i][map[i][j]] = 1;
                    col[j][map[i][j]] = 1;
                    arr[k][map[i][j]] = 1;
                }
                else
                {
                    keep[t][0] = i;
                    keep[t++][1] = j;
                }
            }
        }
        num = t;
        t = 0;
        dfs(keep[t][0],keep[t][1]);
    }
   return 0;
}