用udebug的数据测试了一下应该复杂度没什么问题，求大佬看看是不是哪里死循环了

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
//一次bfs
ll n, m, cnt;
ll head[200005];
ll nxt[400005];
ll to[400005];
ll val[400005];
ll dp[200005];
string save[200005];
bool vis[200005];
inline int read()
{
    int x = 0, f = 1;
    char c = getchar();
    while (c < '0' || c > '9')
    {
        if (c == '-')
            f = -1;
        c = getchar();
    }
    while (c >= '0' && c <= '9')
    {
        x = (x << 1) + (x << 3) + (c ^ 48);
        c = getchar();
    }
    return x * f;
}
inline void add(ll u, ll v, ll w) {
    cnt++;
    nxt[cnt] = head[u];
    to[cnt] = v;
    val[cnt] = w;
    head[u] = cnt;
}
queue<ll> q;
inline void bfs() {
    q.push(n);
    dp[n] = 0;
    vis[n] = true;
    while (!q.empty()) {
        ll u = q.front();
        q.pop();
        vis[u] = false;
        for (ll i = head[u]; i; i = nxt[i]) {
            ll v = to[i];
            if (dp[v] == -1 || dp[v] >= dp[u] + 1) {
                dp[v] = dp[u] + 1;
                if (save[v] != "")save[v] = min(save[v], to_string(val[i]) + " " + save[u]);
                else
                    save[v] = to_string(val[i]) + " " + save[u];
                if(!vis[v])vis[v]=true,q.push(v);
            }
        }
    }
}

inline void solve() {
    cout << dp[1] << endl;
    if (save[1].back() == ' ')
        save[1].pop_back();
    cout << save[1] << endl;
}
inline void init() {
    cnt = 0;
    memset(vis, 0, sizeof(vis));
    memset(nxt, 0, sizeof(nxt));
    memset(to, 0, sizeof(to));
    for (ll i = 1; i <= n; i++)
        head[i] = 0, save[i] = "", dp[i] = -1;
}
int main()
{
     //freopen("in.txt", "r", stdin);
     //freopen("out.txt", "w", stdout);
    //ios::sync_with_stdio(0);
    //cin.tie(0);
    //cout.tie(0);
    while (cin >> n >> m) {
        init();
        for (ll i = 1; i <= m; i++) {
            ll u, v, w;
            //cin >> u >> v >> w;
            u = read();
            v = read();
            w = read();
            add(u, v, w);
            add(v, u, w);
        }
        bfs();
        solve();
    }
}