WA on #4 (应输出AFK）

#include <bits/stdc++.h>
using namespace std;
const int maxn = 500010;
const int inf = 0x7f7f7f7f;
int n, m, b, cnt, maxk;
int head[maxn], dis[maxn], a[maxn];
bool vis[maxn];
struct edge {
	int to, next, val;
} e[maxn];
void add(int u, int v, int w){
	e[++cnt].next = head[u], e[cnt].to = v, e[cnt].val = w, head[u] = cnt;
}

struct node{
    int dis, pos;
    bool operator < (const node &x) const{
        return x.dis < dis;
    }
};

priority_queue<node> q;

bool Dijkstra(int x){
	if (a[1] > x) return false;
	for (int i = 1; i <= n; i++)
		dis[i] = inf;
	dis[1] = 0;
	q.push((node){0, 1});
	while (!q.empty()){
		node tmp = q.top();
		q.pop();
		int u = tmp.pos, d = tmp.dis;
		if (vis[u]) continue;
		vis[u] = 1;
		for (int i = head[u]; i; i = e[i].next){
			int v = e[i].to;
			if (dis[v] > dis[u] + e[i].val && a[v] <= x){
				dis[v] = dis[u] + e[i].val;
				if(!vis[v]) {
                    q.push((node){dis[v], v});
                }
			}
		}
	}
	if (dis[n] > b) return false;
	return true;
} 
int main(){
	cin >> n >> m >> b;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
		maxk = max(maxk, a[i]);
	}
	for (int i = 1, u, v, w; i <= m; i++){
		cin >> u >> v >> w;
		add (u, v, w); add (v, u, w);
	}
	if (!Dijkstra(inf)){
		cout << "AFK";
		return 0;
	}
	int l = 1, r = maxk, mid = (l + r) >> 1;
	while (l < r){
		memset (vis, 0, sizeof vis);
		memset (dis, 0, sizeof dis);
		if (Dijkstra(mid)){
			r = mid;
		} else {
			l = mid + 1;
		}
		mid = (l + r) >> 1;
	}
	cout << l << endl;
	return 0;
}