NOIP2017宝藏

　　本题目用状态压缩搜索，注意要从0状态开始搜索，否则一些不合法的状态也会一直搜下去，无法进行剪枝。

#include
#include
#include
#include
#include
using namespace std;
const int inf=0x3f3f3f3f;
const int maxn=1<<13;
int f[maxn],l[15],pic[14][14],i,j,n,m;
inline void dfs(int x){
    for(int i=1;i<=n;i++){
    if(!((1<<(i-1))&x))continue;
        for(int j=1;j<=n;j++)
        if((((1<<(j-1))|x)>x)&&pic[i][j]!=inf){
            if(f[x|(1<<(j-1))]>f[x]+l[i]*pic[i][j]){
                f[x|(1<<(j-1))]=f[x]+l[i]*pic[i][j];
                l[j]=l[i]+1;
                dfs(x|(1<<(j-1)));
            }
        } 
    }
}
int main(){
    int  a,b,c;
    memset(f,0x3f,sizeof(f));
    memset(pic,0x3f,sizeof(pic));
    memset(l,0x3f,sizeof(l));
    cin>>n>>m;
    for (i=1;i<=m;++i){
        scanf("%d%d%d",&a,&b,&c);
        pic[a][b]=min(pic[a][b],c);
        pic[b][a]=pic[a][b];
    }
    int ans=inf;
    for(int i=1;i<=n;i++){
        memset(l,0x3f,sizeof(l));
        memset(f,0x3f,sizeof(f));
        l[i]=1;
        f[1<<(i-1)]=0;
        dfs(1<<(i-1));
        ans=min(ans,f[(1<1]);
    }
    cout<return 0; 
}