Shared code

#include<bits/stdc++.h>
using namespace std;
vector<bool>vis;
void dfs(int u,int rooms,vector<int>*graph){
  if(vis[u]){
    return;
  }
  vis[u]=true;
  for(int v:graph[u])dfs(v,rooms,graph);
}
int main(){
  int rooms,tunnels;
  cin>>rooms>>tunnels;
  vis.resize(rooms+1,false);
   vector<int>graph[rooms+1];  
  vector<array<int,3>>Tunnels(tunnels);
  for(int tunnel=0;tunnel<tunnels;tunnel++){
    cin>>Tunnels[tunnel][0]>>Tunnels[tunnel][1]>>Tunnels[tunnel][2];
    graph[Tunnels[tunnel][0]].push_back(Tunnels[tunnel][1]);
  }
  dfs(1,rooms,graph);
  vector<long long> score(rooms+1,-1e17);
  score[1]=0;
   for(int room=1;room<=rooms;room++){
    for(auto &tunnel:Tunnels){
      if(score[tunnel[0]]+tunnel[2]>score[tunnel[1]] and vis[tunnel[0]]){
        score[tunnel[1]]=score[tunnel[0]]+tunnel[2];
      }
    }
  }
  long long ans=score[rooms];
   for(int room=1;room<=rooms;room++){
    for(auto &tunnel:Tunnels){
      if(score[tunnel[0]]+tunnel[2]>score[tunnel[1]] and vis[tunnel[0]]){
        score[tunnel[1]]=1e18;
      }
    }
  } 
  if(score[rooms]!=ans){
    cout<<-1;
  }else{
    cout<<ans;
  }
  return 0;
}