这是我滴代码，究竟是什么原因。不开氧气也只能90

#include <bits/stdc++.h>

using namespace std;

const int N = 100000;
const int INF = 0x3f3f3f3f;

int n; int m; int k;
int h[N], e[N], ne[N], w[N], idx;
int dist[N];
bool st[N];

void add(int a, int b, int c)
{
    e[idx] = b;
    ne[idx] = h[a];
    w[idx] = c;
    h[a] = idx ++ ;
}

int SPFA(int s)
{
    memset(dist, 0x3f, sizeof(dist));
    dist[s] = 0;
    st[s] = true;
    queue<int> q;
    q.push(s);

    while (!q.empty())
    {
        int u = q.front(); q.pop();
        st[u] = false;

        for (register int i = h[u]; i != -1; i = ne[i])
        {
            int v = e[i];
            if (dist[v] > dist[u] + w[i])
            {
                dist[v] = dist[u] + w[i];
                if (!st[v])
                {
                    q.push(v);
                    st[v] = true;
                }
            }
        }
    }
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    memset(h, -1, sizeof(h));

    cin >> n >> m >> k;
    for (register int i = 1; i <= m; i ++ )
    {
        int u, v, w;
        cin >> u >> v >> w;
        add(u, v, w), add(v, u, w);
        for (int j = 1; j <= k; j ++ )
        {
            add(u + (j - 1) * n, v + j * n, w / 2);
            add(v + (j - 1) * n, u + j * n, w / 2);
            add(u + j * n, v + j * n, w);
            add(v + j * n, u + j * n, w);
        }
    }

    for (register int i = 1; i <= k; i ++ ) 
        add(n + (i - 1) * n, n + i * n, 0);

    SPFA(1);

    cout << dist[n + k * n] << endl;

    return 0;
}