洛谷 3959 宝藏 NOIP2017提高组Day2 T2

【题解】

　　状压DP. f[i]表示现在的点是否连接的状态是i.

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #define LL long long
 #define rg register
 #define N 5000
 #define inf (0X7f7f7f7f)
 using namespace std;
 int n,m,ans=2e9,f[N],dis[],w[N][N];
 inline int read(){
     int k=,f=; char c=getchar();
     while(c<''||c>'')c=='-'&&(f=-),c=getchar();
     while(''<=c&&c<='')k=k*+c-'',c=getchar();
     return k*f;
 }
 void dfs(int x){
     for(rg int i=;i<=n;i++)if(<<(i-)&x)
         for(rg int j=;j<=n;j++)if(w[i][j]!=inf&&(<<(j-)&x)==)
             if(f[x|(<<(j-))]>f[x]+dis[i]*w[i][j]){
                 int d=dis[j];
                 dis[j]=dis[i]+;
                 f[x|(<<(j-))]=f[x]+dis[i]*w[i][j];
                 dfs(x|(<<(j-)));
                 dis[j]=d;
             }
 }
 int main(){
     n=read(); m=read();
     memset(w,inf,sizeof(w));
     for(rg int i=;i<=m;i++){
         int u=read(),v=read(),d=read();
         w[u][v]=w[v][u]=min(w[u][v],d);
     }
     for(rg int i=;i<=n;i++){
         memset(f,inf,sizeof(f));
         memset(dis,inf,sizeof(dis));
         dis[i]=; f[<<(i-)]=;
         dfs(<<(i-));
         ans=min(ans,f[(<<n)-]);
     }
     printf("%d\n",ans);
     return ;
 }