宝藏

好累啊，不想写题目大意了，放个链接吧。
算法：类似于最小生成树的DP写法（其实一毛一样），预处理转移后直接转移
代码：

#include<bits/stdc++.h>
#define INF 100000000
#define maxn 12
using namespace std;

int n,m,mat[maxn+5][maxn+5];
int w[maxn+5][1<<maxn];
int dp[maxn+5][1<<maxn];
int tot,change[600007][3];
int res=INF;

void dfs(int from,int to,int pos){
	if (pos>n){
		change[++tot][0]=from;
		change[tot][1]=to;
		return;
	}
	dfs(from+(1<<pos-1),to+(1<<pos-1),pos+1);
	dfs(from,to,pos+1);
	dfs(from,to+(1<<pos-1),pos+1);
}

int bitget(int x,int pos){
	return (x>>pos)&1; 
}

int main(){
	scanf("%d%d", &n, &m);
	for (int i=1; i<=n; i++)
		for (int j=1; j<=n; j++)
			mat[i][j]=INF;
	while (m--){
		int u,v,cost;
		scanf("%d%d%d", &u, &v, &cost);
		mat[u][v]=min(mat[u][v],cost);
		mat[v][u]=mat[u][v];
	}
	for (int sta=0; sta<(1<<n); sta++)
		for (int i=1; i<=n; i++){
			w[i][sta]=INF;
			for (int j=1; j<=n; j++)
				if ((sta>>j-1)&1) w[i][sta]=min(w[i][sta],mat[i][j]);
		}
	dfs(0,0,1);
	for (int k=1; k<=tot; k++)
		for (int i=1; i<=n; i++)
			if (bitget(change[k][0],i-1)==0 && bitget(change[k][1],i-1)==1) 
				if (change[k][2]<INF) change[k][2]+=w[i][change[k][0]];
	for (int i=0; i<=n; i++)
		for (int sta=0; sta<(1<<n); sta++) dp[i][sta]=INF;
	for (int sta=1; sta<(1<<n); sta<<=1) dp[0][sta]=0;
	for (int i=1; i<=n; i++){
		for (int k=1; k<=tot; k++)
			dp[i][change[k][1]]=min(dp[i][change[k][1]],dp[i-1][change[k][0]]+change[k][2]*i);
		res=min(res,dp[i][(1<<n)-1]);
	}
	printf("%d
",res);
	return 0;
}