[ZOJ 1008]Gnome Tetravex (dfs搜索 + 小优化)

 1 #include <cstdio>
 2 #include <cstdlib>
 3 #include <string>
 4 #include <iostream>
 5 #include <cstring>
 6 #include <algorithm>
 7 #include <cctype>
 8 #include <vector>
 9 #include <map>
10 #include <set>
11 #include <iterator>
12 #include <functional>
13 #include <cmath>
14 #include <numeric>
15 #include <ctime>
16 using namespace std;
17 typedef long long LL;
18 typedef pair<int,int> PII;
19 typedef vector<int> VI;
20 #define PB push_back
21 #define MP make_pair
22 #define SZ size()
23 #define CL clear()
24 #define AA first
25 #define BB second
26 #define EPS 1e-8
27 #define ZERO(x) memset((x),0,sizeof(x))
28 const int INF = ~0U>>1;
29 const double PI = acos(-1.0);
30 
31 int n;
32 int now[10][10];
33 bool vis[100];
34 int ptr;
35 bool flag;
36 
37 struct Node{
38     int top,right,bottom,left;
39     int num;
40     bool operator==(const Node& b) const{
41         return top==b.top&&right==b.right&&bottom==b.bottom&&left==b.left;
42     }
43     Node(int t=0,int r=0,int b=0,int l=0):top(t),right(r),bottom(b),left(l){}
44 };
45 Node mp[100];
46 
47 void dfs(int x,int y){
48     if(flag) return;
49     if( x==n || y==n ){
50         flag = true;
51         return;
52     }
53     for(int i=0;i<ptr;i++){
54         if( mp[i].num&&
55            (x==0||mp[now[x-1][y]].bottom==mp[i].top)
56            &&(y==0||mp[now[x][y-1]].right==mp[i].left) ){
57                 now[x][y] = i;
58                 mp[i].num--;
59                 if( y+1<n ) dfs(x,y+1);
60                 else dfs(x+1,0);
61                 mp[i].num++;
62            }
63     }
64 }
65 
66 int main(){
67     int kase = 1;
68     while(scanf("%d",&n),n){
69         ptr = 0;
70         for(int i=0;i<n*n;i++){
71             int t,r,b,l;
72             scanf("%d%d%d%d",&t,&r,&b,&l);
73             bool appear = 0;
74             for(int j=0;j<ptr;j++){
75                 if(Node(t,r,b,l)==mp[j]){
76                     mp[j].num++;
77                     appear = 1;
78                 }
79             }
80             if(!appear){
81                 mp[ptr] = Node(t,r,b,l);
82                 mp[ptr++].num = 1;
83             }
84         }
85 
86         flag = false;
87         dfs(0,0);
88 
89         if(kase!=1) puts("");
90         printf("Game %d: ",kase++);
91         puts(flag?"Possible":"Impossible");
92     }
93     return 0;
94 }