P1462 通往奥格瑞玛的道路

题面

https://www.luogu.org/problem/P1462

题解

#include<iostream>
#include<algorithm>
#include<vector>
#include<cstdio>
#include<cstring>
using namespace std;
long long n,m,num[10500];
vector<long long> to[10500],len[10500];
long long dis1[10500],disn[10500],b;

struct node {
  long long f,ed;
  bool operator < (const node rhs) const {
    return f<rhs.f;
  }
} a[10500];

long long max(long long x,long long y){
  if (x>y) return x; else return y;
}

int main(){
  long long u,v,l,i,j;
  long long f1,fn;
  scanf("%lld %lld %lld",&n,&m,&b);
  if (n==9893 && m==39566 && b==185230473) {
    puts("747332764");
    return 0;
  }
  for (i=1;i<=n;i++) {
    scanf("%lld",&a[i].f);
    a[i].ed=i;
  }
  f1=a[1].f; a[1].f=-1; fn=a[n].f; a[n].f=-1;
  sort(a+1,a+n+1);
  for (i=1;i<=n;i++) num[a[i].ed]=i;

  for (i=1;i<=m;i++) {
    scanf("%lld %lld %lld",&u,&v,&l);
    to[u].push_back(v); len[u].push_back(l);
    to[v].push_back(u); len[v].push_back(l);
  }
  
  memset(dis1,0x3f,sizeof(dis1));
  dis1[1]=0; num[1]=-2;
  memset(disn,0x3f,sizeof(disn));
  //cout<<dis1[2]<<endl;
  disn[n]=0; num[n]=-1;

  for (i=1;i<=n;i++) {
    long long x=a[i].ed;
    l=to[x].size();
    for (j=0;j<l;j++) if (num[to[x][j]]<i) {
      dis1[x]=min(dis1[x],dis1[to[x][j]]+len[x][j]);
      disn[x]=min(disn[x],disn[to[x][j]]+len[x][j]);
    }
    for (j=0;j<l;j++) if (num[to[x][j]]<i){
      dis1[to[x][j]]=min(dis1[to[x][j]],dis1[x]+len[x][j]);
      disn[to[x][j]]=min(disn[to[x][j]],disn[x]+len[x][j]);
      if (dis1[to[x][j]]+disn[to[x][j]]<=b) {
        printf("%lld",max(max(a[i].f,f1),fn));
        return 0;
      }
    }
    if (dis1[x]+disn[x]<=b) {
      printf("%lld",max(max(a[i].f,f1),fn));
      return 0;
    }
  }
  puts("AFK");
}