Luo Gu P1462 road to Orgrimmar-half answer, dijkstra for the most short stack optimization

Each city will be required to answer tolls on the array, sort, find the location of the start and end of the largest tolls, as the left half of the industry, all the cities in the largest tolls as half of the right boundary. An upper limit for each election spending, consumption above this city can not choose, dijkstra find a minimum consumption of blood that is the shortest route, look at the spending limit as it takes, can not come to the end of blood is higher than 0, if r = mid, reduce the consumption limit, if not, l = mid + 1, increasing the maximum consumption, the code is affixed.

#include <bits/stdc++.h>
using namespace std;
const int maxn=1e4+5;
const int maxm=1e5+5;
const int inf=1e9+7;
struct que
{
    int key,value;
    friend bool operator < (que a,que b)
    {
        return a.value > b.value;
    }
};
priority_queue<que>q;
struct node
{
    int to,next,len;
}p[maxm];
int head[maxn];
int a[maxn],b[maxn];
int vertex[maxn];
bool vis[maxn];
int n,m,c;
int cnt,ans;
void add(int x,int y,int w)
{
    p[++cnt].next=head[x];
    p[cnt].to=y;
    p[cnt].len=w;
    head[x]=cnt;
}
bool check(int top)
{
    if(top<a[1])
    return false;
    for(int i=2;i<=n;i++)
    vertex[i]=inf,vis[i]=false;
    vis[1]=true;
    for(int i=head[1];i;i=p[i].next)
    {
        int v=p[i].to;
        //cout<<v<<endl;
        int cost=p[i].len;
        //cout<<cost<<endl;
        if(vertex[v]>cost&&a[v]<=top)
        {
            //cout<<a[v]<<endl;
            vertex[v]=cost;
            q.push({v,cost});
        }
    }
    while(!q.empty())
    {
        que temp=q.top();
        q.pop();
        if(vis[temp.key])
        continue;
        vis[temp.key]=true;
        for(int i=head[temp.key];i;i=p[i].next)
        {
            int v=p[i].to;
            int cost=p[i].len;
            if(a[v]<=top&&(vertex[v]>(temp.value+cost))&&!vis[v])
            {
                vertex[v]=temp.value+cost;
                q.push({v,vertex[v]});
            }
        }
    }
    if(c-vertex[n]>0)
    return true;
    else
    return false;
}
int main()
{
    scanf("%d %d %d",&n,&m,&c);
    int l,r,mid;
    for(int i=1;i<=n;i++)
    scanf("%d",&a[i]),b[i]=a[i];
    int t1=a[1],t2=a[n];
    sort(b+1,b+1+n);
    int Ma=-1;
    for(int i=1;i<=n;i++)
    if(b[i]==t1||b[i]==t2)
    {
        if(Ma<b[i])
        Ma=b[i],l=i;
    }
    r=n;
    for(int i=1;i<=m;i++)
    {
        int x,y,w;
        scanf("%d %d %d",&x,&y,&w);
        add(x,y,w);
        add(y,x,w);
    }
    //cout<<b[n]<<endl;
    //check(b[n]);
    //printf("%d\n",vertex[n]);
    if(!check(b[n]))
    {
        puts("AFK");
        return 0;
    }
    ans=b[n];
    while(l<r)
    {
        mid=(l+r)>>1;
        int top=b[mid];
        if(check(top))
        r=mid,ans=top;
        else
        l=mid+1;
    }
    printf("%d\n",ans);
    return 0;
}