跪求dalao挑错Orz，代码应该能看懂

#include<bits/stdc++.h>
#define maxn 10100 
#define maxm 50100 
using namespace std;
typedef long long ll;
int n, m, head[maxn], vis[maxn], cnt;
ll b, cost[maxn], a[maxn], l, r, mid, ans;

struct edge{
    int to, nxt;
    ll w;
}e[maxm<<1];

inline void add(int u, int v, ll d){
    e[++cnt].to = v;
    e[cnt].w = d;
    e[cnt].nxt = head[u];
    head[u] = cnt;
}

bool SPFA(ll lim){ //经过的城市最大不得超过lim 
    queue <int> q;
    memset(vis, 0, sizeof(vis));
    memset(cost, 0x7f, sizeof(cost));
    cost[1] = 0;
    q.push(1);
    vis[1] = 1;

    while(q.size()){
        int u = q.front();
        q.pop();
        for(int i=head[u] ; i ; i=e[i].nxt){
            int v = e[i].to;
            ll d = e[i].w;
            if(a[v] > lim) continue; //超过lim，不能走 
            if(cost[v] > cost[u] + d){
                cost[v] = cost[u] + d;
                if(!vis[v]){
                    q.push(v);
                    vis[v] = 1;
                }
            } 
        }
        vis[u] = 0;
    }

    if(cost[n] < b) return true; //还可以进一步放宽限制 
    return false;
}

int main(){
    scanf("%d%d%lld", &n, &m, &b);
    for(int i=1 ; i<=n ; i++){
        scanf("%lld", &a[i]);
        r = max(r, a[i]);
    }
    l = max(a[1], a[n]), ++r;

    for(int i=1 ; i<=m ; i++){
        int x, y; ll z;
        scanf("%d%d%lld", &x, &y, &z);
        add(x, y, z);
        add(y, x, z);
    }

    if(!SPFA(r)){
        puts("AFK");
        return 0;
    }

    while(l < r){
        mid = (l + r)>>1;
        if(SPFA(mid)) ans = mid, l = mid + 1; //放宽最大花费，让城市变多 
        else r = mid;
    }

    printf("%lld\n", ans);
    return 0;
}