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[][],col[][],arr[][];//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[][],map[][],num,t;      //keep[][]记录可填数的位置;
 void show()
 {
     for (int i = ;i < ;i ++)
     {
         for (int j = ;j < ;j ++)
         {
             printf("%d",map[i][j]);
         }
         puts("");
     }
 }
 int dfs(int x,int y)
 {
     if (t==num)
     {
         show();
         return ;
     }
     for (int i = ;i <= ;i ++)
     {
         int k = x/*+y/;
         if (!row[x][i]&&!col[y][i]&&!arr[k][i])
         {
             map[x][y] = i;
             row[x][i] = ;
             col[y][i] = ;
             arr[k][i] = ;
             ++t;
             if (dfs(keep[t][],keep[t][]))
             return ;
             --t;
             //回溯过程中，清除标记
             map[x][y] = ;
             row[x][i] = ;
             col[y][i] = ;
             arr[k][i] = ;

         }
     }
     return ;

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