zju1002

棋盘上放置房屋问题

#include<iostream>

using namespace std;

 

inline int max(int a,int b)

{

       if(a>=b) return a; else return b;

}

inline int min(int a,int b)

{

       if(a<=b) return a; else return b;

}

 

int board[4][4];

 

typedef struct point{

       int x;

       int y;

}point;

 

point house[16];

int n;

int max_house;

int cur_house;

 

 

 

void init()

{

       cur_house=max_house=0;

}

 

int check(int r,int c)

{    

       int i,j;

       bool flag;

       for(i=0;i<cur_house;i++)

       {

              flag=true;

              if(house[i].x==r)

              {

                     flag=false;

                     for(j=min(house[i].y,c); j<=max(house[i].y,c); j++)

                     {

                            if(board[r][j]==1)

                                   flag=true;

                     }

              }

              else if(house[i].y==c)

              {

                     flag=false;

                 

                    

                      for(j=min(house[i].x,r); j<=max(house[i].x,r); j++)

                      {

                               if(board[j][c]==1)

                                      flag=true;

                      }

                    

              }

              if(flag==false)

              {

                     return 0;

              }

       }

 

       return 1;

}

 

void dfs(int level)

{

       if(level>=n*n)

       {

              if(cur_house>max_house)

                     max_house=cur_house;

              return;

       }

       if(board[level/n][level%n]==1)

       {

              dfs(level+1);

       }

       else

       {

              if( check(level/n,level%n)==1 )//检查这一格是否能放房子

              {

                     house[cur_house].x=level/n;

                     house[cur_house].y=level%n;

                     cur_house++;

                     dfs(level+1);

                     cur_house--;

              }

              if(cur_house+(n*n-(level+1)) > max_house )

                 dfs(level+1);

       }

}

 

 

int main()

{

 

      

       char ch;

       cin>>n;

       while(n!=0)

       {

           for(int i=0;i<n;i++)

                  for(int j=0;j<n;j++)

                     {

                        cin>>ch;

                     if(ch=='X')

                              board[i][j]=1;

                        else board[i][j]=0;

                     }

              init();

              dfs(0);

              cout<<max_house<<endl;

              cin>>n;

       }

       return 0;

}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#include<iostream>

using namespace std;

 

inline int max(int a,int b)

{

       if(a>=b) return a; else return b;

}

inline int min(int a,int b)

{

       if(a<=b) return a; else return b;

}

 

int board[4][4];

 

typedef struct point{

       int x;

       int y;

}point;

 

point house[16];

int   path[16];

int n;

int max_house;

int cur_house;

 

 

 

void init()

{

       cur_house=max_house=0;

}

 

int check(int r,int c)

{    

       int i,j;

       bool flag;

       for(i=0;i<cur_house;i++)

       {

              flag=true;

              if(house[i].x==r)

              {

                     flag=false;

                     for(j=min(house[i].y,c); j<=max(house[i].y,c); j++)

                     {

                            if(board[r][j]==1)

                                   flag=true;

                     }

              }

              else if(house[i].y==c)

              {

                     flag=false;

                 

                    

                      for(j=min(house[i].x,r); j<=max(house[i].x,r); j++)

                      {

                               if(board[j][c]==1)

                                      flag=true;

                      }

                    

              }

              if(flag==false)

              {

                     return 0;

              }

       }

 

       return 1;

}

 

 

 

void trackback()

{

       int level=0;

 

       while(true)

       {

              while(board[level/n][level%n]==0 && level<n*n && check(level/n,level%n)==1)

              {

                     house[cur_house].x=level/n;

                     house[cur_house].y=level%n;

                     cur_house++;

                     path[level]=1;

                     level++;

              }

 

              if(level>=n*n)

              {

                     if(cur_house>max_house)

                     {

                            max_house=cur_house;

                     }

 

              }

              else

              {

                     path[level]=0;

                     level++;

              }

 

 

              while(cur_house+(n*n-level)<=max_house)

              {    

                     level--;

                     while(level>=0 && path[level]==0)

                     {

                            level--;

                     }

                     if(level<0)

                            return ;

                     else

                     {

 

                               cur_house--;

                               path[level]=0;

                               level++;

                     }

              }

       }

}

 

int main()

{

 

      

       char ch;

       cin>>n;

       while(n!=0)

       {

           for(int i=0;i<n;i++)

                  for(int j=0;j<n;j++)

                     {

                        cin>>ch;

                     if(ch=='X')

                              board[i][j]=1;

                        else board[i][j]=0;

                     }

              init();

              trackback();

              cout<<max_house<<endl;

              cin>>n;

       }

       return 0;

}

 

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