Union Find and search

1.POJ2488　　A Knight's Journey

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 #include<iostream>
 #include<cstring>
 #include<algorithm>
 #include<string>
 using namespace std;

 #define N 27
 #define INF 0x7FFFFFFF
 int p,q,_count=;
 int _dec[N][N];
 int routine[*N];
 int t1,t2;
 int flag,flag2;

 void path(int x,int y,int k)
 {
     switch (k)
     {
     case :{t1 = x-;t2 = y-;break;}
     case :{t1 = x+;t2 = y-;break;}
     case :{t1 = x-;t2 = y-;break;}
     case :{t1 = x+;t2 = y-;break;}
     case :{t1 = x-;t2 = y+;break;}
     case :{t1 = x+;t2 = y+;break;}
     case :{t1 = x-;t2 = y+;break;}
     case :{t1 = x+;t2 = y+;break;}
     }
 }
 void OUTPUT()
 {
     for (int i=;i<_count;i++)
     {
         cout<<(char)('A'+routine[*i+])<<routine[*i]+;
         if (i==_count-) cout<<endl;
     }
 }
 bool DFS(int x,int y)
 {
     if (flag2 == ) return ;
     _dec[x][y]=;
     routine[*_count]=x;
     routine[*_count+]=y;
     _count++;
     if (_count>p*q)
     {
         flag2 = ;
         return ;
     }
     if ((_count == p*q)&&(flag == ))
     {
         OUTPUT();
         flag = ;
         return ;
     }
     for (int k=;k<;k++)
     {
         path(x,y,k);
         int xx=t1,yy = t2;
         if ((xx>=)&&(xx<p)&&(yy>=)&&(yy<q)&&(_dec[xx][yy]==))
             if (DFS(xx,yy)) return ;
     }
     _dec[x][y]=;
     _count--;
     return ;
 }
 int main()
 {
     int n;
     cin>>n;
     for (int m=;m<=n;m++)
     {
         for (int i=;i<N;i++)
             for (int j=;j<N;j++)
                 _dec[i][j]=;
         memset(routine,,sizeof(routine));
         cin>>p>>q;
         cout<<"Scenario #"<<m<<":"<<endl;
         if ((p==)&&(q==))
         {
             cout<<"A1"<<endl<<endl;
             continue;
         }
         if (p*q> || p>= || q>= || p<= || q<=)
         {
             cout<<"impossible"<<endl<<endl;
             continue;
         }
         _count = ;
         flag = ;
         flag2 = ;
         DFS(,);
         if ((flag2 == )||(flag==)) cout<<"impossible"<<endl;
         cout<<endl;
     }
     return ;
 }

2.POJ 1077 Eight

http://blog.csdn.net/whyorwhnt/article/details/10555989