POJ 2676 Sudoku

 

//这是一个数独，我选择用dfs从（1，1）点蛇形搜索下去，到达（9，9）就停止。

//当然有更好的方法，dancing-links

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
int a[10][10],f[4][4][10],ff,lin[10][10],col[10][10];       
void dfs(int x,int y)
{
    if(ff)return;
 if(!a[x][y])
 {
    for(int i=1;i<=9;i++)
    if(!f[(x-1)/3+1][(y-1)/3+1][i])
        {
   if(lin[x][i]||col[y][i])continue;
            if(ff)return;
            a[x][y]=i;
            lin[x][i]=1;col[y][i]=1;
            f[(x-1)/3+1][(y-1)/3+1][i]=1;
            if(x==9&&y==9)
       {
     ff=1;return;
    }
            if(y%2&&x==9)dfs(x,y+1);
            else if(y%2==0&&x==1)dfs(x,y+1);
            else if(y%2)dfs(x+1,y);
            else dfs(x-1,y);
            if(ff)return;
            a[x][y]=0;
            lin[x][i]=0;col[y][i]=0;
            f[(x-1)/3+1][(y-1)/3+1][i]=0;
        }
 }
 else{ if(x==9&&y==9)
    {
     ff=1;return;
    }
     if(y%2&&x==9)dfs(x,y+1);
            else if(y%2==0&&x==1)dfs(x,y+1);
            else if(y%2)dfs(x+1,y);
            else dfs(x-1,y);
 }
}
int main()
{
    //freopen("1.txt","r",stdin);
    int T,i,j;
    cin>>T;
 char s[10];
    while(T--)
    {
        ff=0;
        memset(lin,0,sizeof(lin));
  memset(col,0,sizeof(col));
        memset(f,0,sizeof(f));
        for(i=1;i<=9;i++)
  {
   cin>>s;
            for(j=1;j<=9;j++)
                {
                    a[i][j]=s[j-1]-'0';
                    if(a[i][j])
                    {
                        lin[i][a[i][j]]=1;
      col[j][a[i][j]]=1;
      f[(i-1)/3+1][(j-1)/3+1][a[i][j]]=1;
                    }
                }
  }
         dfs(1,1);
         for(i=1;i<=9;i++)
            {for(j=1;j<=9;j++)
            cout<<a[i][j];   cout<<endl;}
    }
    return 0;
}