80分求助

#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>
#include <vector>
#include <climits>

using namespace std;
typedef long long LL;
typedef pair<LL,int> PII;
const int N = 1e4 + 10,M = 1e5 + 10;
const LL INF = LLONG_MAX / 3;
int h[N],e[M],ne[M],idx;
LL dist[N],f[N],w[M],b;
int n,m;
LL l,r;
bool st[N];

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

bool check(LL x)
{
    if(f[1] > x) return false;
    priority_queue<PII,vector<PII>,greater<PII>> heap;
    heap.push({0,1});
    dist[1] = 0;
    while(heap.size())
    {
        auto u = heap.top();heap.pop();
        int v = u.second;
        if(st[v]) continue;
        st[v] = true;
        for(int i = h[v];i != -1;i = ne[i])
        {
            int j = e[i];
            if(f[j] <= x && dist[j] > dist[v] + w[i])
            {
                dist[j] = dist[v] + w[i];
                heap.push({dist[j],j});
            }
        }
    }
    if(dist[n] <= b) return true;
    return false;
}

int main()
{
    cin >> n >> m >> b;
    memset(h,-1,sizeof h);
    for(int i = 1;i <= n;i ++) dist[i] = INF;
    for(int i = 1;i <= n;i ++) 
    {
        cin >> f[i];
        r = max(r,f[i]);
    }
    l = max(f[1],f[n]);
    for(int i = 0;i < m;i ++)
    {
        int a,b;LL c;cin >> a >> b >> c;
        add(a,b,c);
        add(b,a,c);
    }

    if(!check(INF)) puts("AFK");
    else
    {
        while(l < r)
        {
            LL mid = l + r >> 1;
            if(check(mid)) r = mid;
            else l = mid + 1;
        }
        cout << r << endl;
    }
    return 0;
}