Union Find and search

1.POJ2488　　A Knight's Journey
 1 #include<iostream>
 2 #include<cstring>
 3 #include<algorithm>
 4 #include<string>
 5 using namespace std;
 6 
 7 #define N 27
 8 #define INF 0x7FFFFFFF
 9 int p,q,_count=0;
10 int _dec[N][N];
11 int routine[2*N];
12 int t1,t2;
13 int flag,flag2;
14 
15 void path(int x,int y,int k)
16 {
17     switch (k)
18     {
19     case 0:{t1 = x-1;t2 = y-2;break;}
20     case 1:{t1 = x+1;t2 = y-2;break;}
21     case 2:{t1 = x-2;t2 = y-1;break;}
22     case 3:{t1 = x+2;t2 = y-1;break;}
23     case 4:{t1 = x-2;t2 = y+1;break;}
24     case 5:{t1 = x+2;t2 = y+1;break;}
25     case 6:{t1 = x-1;t2 = y+2;break;}
26     case 7:{t1 = x+1;t2 = y+2;break;}
27     }
28 }
29 void OUTPUT()
30 {
31     for (int i=0;i<_count;i++)
32     {
33         cout<<(char)('A'+routine[2*i+1])<<routine[2*i]+1;
34         if (i==_count-1) cout<<endl;
35     }
36 }
37 bool DFS(int x,int y)
38 {
39     if (flag2 == 1) return 0;
40     _dec[x][y]=1;
41     routine[2*_count]=x;
42     routine[2*_count+1]=y;
43     _count++;
44     if (_count>p*q)
45     {
46         flag2 = 1;
47         return 0;
48     }
49     if ((_count == p*q)&&(flag == 0))
50     {
51         OUTPUT();
52         flag = 1;
53         return 1;
54     }
55     for (int k=0;k<8;k++)
56     {
57         path(x,y,k);
58         int xx=t1,yy = t2;
59         if ((xx>=0)&&(xx<p)&&(yy>=0)&&(yy<q)&&(_dec[xx][yy]==0))    
60             if (DFS(xx,yy)) return 1;
61     }
62     _dec[x][y]=0;
63     _count--;
64     return 0;
65 }
66 int main()
67 {
68     int n;
69     cin>>n;
70     for (int m=1;m<=n;m++)
71     {
72         for (int i=0;i<N;i++)
73             for (int j=0;j<N;j++)
74                 _dec[i][j]=0;
75         memset(routine,0,sizeof(routine));
76         cin>>p>>q;
77         cout<<"Scenario #"<<m<<":"<<endl;
78         if ((p==1)&&(q==1))
79         {
80             cout<<"A1"<<endl<<endl;
81             continue;
82         }
83         if (p*q>26 || p>=9 || q>=9 || p<=2 || q<=2)
84         {
85             cout<<"impossible"<<endl<<endl;
86             continue;
87         }
88         _count = 0;
89         flag = 0;
90         flag2 = 0;
91         DFS(0,0);
92         if ((flag2 == 1)||(flag==0)) cout<<"impossible"<<endl;
93         cout<<endl;
94     }
95     return 0;
96 }
View Code
2.POJ 1077 Eight
http://blog.csdn.net/whyorwhnt/article/details/10555989