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.
1 #include<cstdio> 2 #include<cstring> 3 #include<algorithm> 4 #define LL long long 5 #define rg register 6 #define N 5000 7 #define inf (0X7f7f7f7f) 8 using namespace std; 9 int n,m,ans=2e9,f[N],dis[20],w[N][N]; 10 inline int read(){ 11 int k=0,f=1; char c=getchar(); 12 while(c<'0'||c>'9')c=='-'&&(f=-1),c=getchar(); 13 while('0'<=c&&c<='9')k=k*10+c-'0',c=getchar(); 14 return k*f; 15 } 16 void dfs(int x){ 17 for(rg int i=1;i<=n;i++)if(1<<(i-1)&x) 18 for(rg int j=1;j<=n;j++)if(w[i][j]!=inf&&(1<<(j-1)&x)==0) 19 if(f[x|(1<<(j-1))]>f[x]+dis[i]*w[i][j]){ 20 int d=dis[j]; 21 dis[j]=dis[i]+1; 22 f[x|(1<<(j-1))]=f[x]+dis[i]*w[i][j]; 23 dfs(x|(1<<(j-1))); 24 dis[j]=d; 25 } 26 } 27 int main(){ 28 n=read(); m=read(); 29 memset(w,inf,sizeof(w)); 30 for(rg int i=1;i<=m;i++){ 31 int u=read(),v=read(),d=read(); 32 w[u][v]=w[v][u]=min(w[u][v],d); 33 } 34 for(rg int i=1;i<=n;i++){ 35 memset(f,inf,sizeof(f)); 36 memset(dis,inf,sizeof(dis)); 37 dis[i]=1; f[1<<(i-1)]=0; 38 dfs(1<<(i-1)); 39 ans=min(ans,f[(1<<n)-1]); 40 } 41 printf("%d\n",ans); 42 return 0; 43 }
