hdu 4272 2012长春赛区网络赛 dfs暴力 ***

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<cmath>
 6 #include<queue>
 7 #include<map>
 8 using namespace std;
 9 #define MOD 1000000007
10 const int INF=0x3f3f3f3f;
11 const double eps=1e-5;
12 typedef long long ll;
13 #define cl(a) memset(a,0,sizeof(a))
14 #define ts printf("*****\n");
15 const int MAXN=1005;
16 int n,m,tt;
17 bool vis[MAXN];
18 int a[MAXN];
19 bool dfs(int pos)
20 {
21     while(vis[pos]==1&&pos>0)   pos--;
22     if(pos==0)  return 1;
23     if(pos==1)
24     {
25         return 0;
26     }
27     int temp=pos-1;
28     for(int i=0;i<=5;i++)
29     {
30         if(temp<=0) return 0;
31         if(vis[temp])
32         {
33             i--;
34             temp--;
35             continue;
36         }
37         if(a[pos]==a[temp]) //找到
38         {
39             vis[temp]=1;
40             if(dfs(pos-1))  return 1;
41             vis[temp]=0;
42         }
43         temp--;
44     }
45     return 0;
46 }
47 int main()
48 {
49     int i,j,k,ca=1;
50     #ifndef ONLINE_JUDGE
51     freopen("1.in","r",stdin);
52     #endif
53     while(scanf("%d",&n)!=EOF)
54     {
55         map<int,int> mp;
56         for(i=1;i<=n;i++)
57         {
58             scanf("%d",a+i);
59             mp[a[i]]++;
60         }
61         if(n%2)
62         {
63             printf("0\n");
64             continue;
65         }
66         bool f=1;
67         map<int,int>::iterator it;
68         for(it=mp.begin();it!=mp.end();it++)
69         {
70             if((it->second)%2==1)
71             {
72                 f=0;
73                 break;
74             }
75         }
76         if(!f)
77         {
78             printf("0\n");
79             continue;
80         }
81         cl(vis);
82         printf("%d\n",dfs(n));
83     }
84 }