//Illustration Attached. -KrisXJ 8-3
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
const int MAXN=15;
const ll INF=1145141919810007210;

int n,m;
ll G[MAXN+1][MAXN+1];

int main()
{
    cin>>n>>m;
    for(int i = 1;i <= n;i++)
        for(int j = 1;j <= n;j++)
            G[i][j]=(i == j) ? 0 : INF;
            
    for(int i = 0;i < m;i++)
    {
        int u,v,w;
        cin>>u>>v>>w;
        if(w<G[u][v])
        {
            G[u][v] = w;
            G[v][u] = w;
        }
    }

    ll ans = INF;
    int full_mask = (1 << n) - 1;

    for(int begin = 1;begin <= n;begin++)
    {
        vector<ll> dp(1<<n,INF); // dp[mask]：当前已开发宝藏屋为mask时的最小代价
        vector<vector<int> > depth(1 << n,vector<int>(n + 1,INF));// depth[mask][u]：mask状态下u的深度

        int init = 1 << (begin-1);
        dp[init] = 0;
        depth[init][begin] = 1;

        for(int mask = init;mask < (1 << n);mask++)
        {
            if(dp[mask] == INF) //这个状态还没有算过
                continue;

            for(int u = 1;u <= n;u++)
            {
                if(!(mask& (1 << (u - 1)))) //u不在当前掩码中
                    continue;
                int d = depth[mask][u];
                if(d == INF)
                    continue;

                for(int v = 1;v<=n;v++)
                {
                    if(u == v)
                        continue;
                    if(mask & (1 << (v - 1)))
                        continue;
                    if(G[u][v] == INF)
                        continue;
					//排除：同一节点、v已处理、不存在边
                    int new_mask=mask | (1 << (v - 1));
                    ll new_cost = dp[mask] + G[u][v] * d;
                    int new_depth = d+1;

                    if(new_cost < dp[new_mask])
                    {
                        dp[new_mask] = new_cost;
                        for(int w =1;w <= n;w++)
                            depth[new_mask][w] = depth[mask][w];
                        depth[new_mask][v] = new_depth;
                    }
                    else if(new_cost == dp[new_mask] && new_depth < depth[new_mask][v])
                        depth[new_mask][v] = new_depth;
                }
            }
        }

        if(dp[full_mask] < ans)
            ans = dp[full_mask];
    }

    cout<<ans;

    return 0;
}

我在一开始使用了上述代码提交，发现只有 Subtask 2 的20个测试点通过。部分思路已注释出。代码的问题在哪里呢?