zoj1002 Fire Net

?

#include<iostream>

#include<string>

#include<cstring>

#include<algorithm>

using namespace std;

string map[5];

int ANS,n;

int wall[5][5],mark[5][5];

bool check(int x,int y)

{

      for(int i=x-1;i>=0;i--)

      {

          if(mark[i][y])return 0;

          if(wall[i][y])break;

      }

      for(int j=y-1;j>=0;j--)

      {

          if(mark[x][j])return 0;

          if(wall[x][j])break;

      }

      for(int i=x+1;i<n;i++)

      {

          if(mark[i][y])return 0;

          if(wall[i][y])break;

      }

      for(int j=y+1;j<n;j++)

      {

          if(mark[x][j])return 0;

          if(wall[x][j])break;

      }

      return 1;

}

void DFS(int num)

{

    if(ANS<num)ANS=num;

    for(int i=0;i<n;i++)//相当于对每个格子进行全排列

        for(int j=0;j<n;j++)

            if(!wall[i][j]&&!mark[i][j]&&check(i,j))

            {

                mark[i][j]=1;

                DFS(num+1);

                mark[i][j]=0;

            }

}

int main()

{

     

    while(cin>>n&&n)

    {

        ANS=0;

        memset(wall,0,sizeof(wall));

        memset(mark,0,sizeof(mark));

        for(int i=0;i<n;i++)

        {

            cin>>map[i];

            for(int j=0;j<n;j++)

                if(map[i][j]=='X')

                {

                    wall[i][j]=1;

                }

        }

        DFS(0);

        cout<<ANS<<endl;

    }

}