JZYZOJ1384 种花小游戏 状压dp

http://172.20.6.3/Problem_Show.asp?id=1384

最开始以为是dfs然后超时了，然后调了半天调成dp，还不如再写一遍。。。

代码

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<cmath>
 6 using namespace std;
 7 const int maxn=1<<25;
 8 int n,x,y;
 9 int a[20][2]={};
10 double f[(1<<16)+10][20]={};
11 int vis[20]={};
12 double ans=(1<<30);
13 int main(){
14     scanf("%d",&n);int x,y;
15     for(int i=0;i<n;i++){
16         scanf("%d%d",&a[i][0],&a[i][1]);
17     }scanf("%d%d",&x,&y);
18     int ma=1<<n;
19     for(int i=1;i<ma;i++){
20         for(int j=0;j<n;j++){
21             f[i][j]=1.0*maxn;
22         }
23     }
24     int x1,x2;double y1,y2,wtf;
25     for(int i=0;i<n;i++){
26         x1=1<<i;
27         y1=(double)abs(a[i][0]-x);y2=(double)abs(a[i][1]-y);
28         wtf=sqrt((double)y1*y1+y2*y2);
29         f[x1][i]=wtf;
30     }int wt=1;
31     for(int i=1;i<ma;i++){
32         if(i==wt){wt*=2;continue;}
33         for(int j=0;j<n;j++){
34             x1=1<<j;if((x1|i)!=i)continue;
35             for(int w=0;w<n;w++){
36                 x2=1<<w;
37                 if((x2|i)!=i||w==j)continue;
38                 y1=(double)abs(a[j][0]-a[w][0]);y2=(double)abs(a[j][1]-a[w][1]);
39                 wtf=sqrt((double)y1*y1+y2*y2);
40                 if(f[i-x1][w]+wtf-f[i][j]<0){
41                     f[i][j]=f[i-x1][w]+wtf;
42                 }
43             }
44         }
45     }double ans=maxn;
46     for(int i=0;i<n;i++){
47         if(f[ma-1][i]<ans)ans=f[ma-1][i];
48     }
49     printf("%.2f",ans);
50     return 0;
51 }