Dijsktra

#include <bits/stdc++.h>
#define TASK "DIJKSTRA"
using namespace std;
const int N = 1e5;
const long long oo = 1e18;
long long d[N + 1], z;
int n, m, x, y;
struct T
{
    int v;
    long long w;
};
struct TQueue
{
    int vertex;
    long long dlab;
    bool operator < (const TQueue& other) const
    {
        return other.dlab < dlab;
    }
    bool Valid() const
    {
        return d[vertex] == dlab;
    }
};
vector<T> Adj[N + 1];
priority_queue<TQueue> PQ;
bool Relax(int u, int v, long long w)
{
    if (d[v] > d[u] + w)
    {
        d[v] = d[u] + w;
        return true;
    }
    return false;
}
void read()
{
   cin >> n >> m;
   fill(d + 2, d + n + 1, oo);
   for (int i = 1; i <= m; ++ i)
   {
       cin >> x >> y >> z;
       Adj[x].push_back({y, z});
   }
}
void solve()
{
   PQ.push({1, 0});
   while (!PQ.empty())
   {
       TQueue r = PQ.top();
       PQ.pop();
       if (!r.Valid())
       {
           continue;
       }
       int u = r.vertex;
       if (u == n)
       {
           break;
       }
       for (const T & a : Adj[u])
       {
           if (Relax(u, a.v, a.w))
           {
               PQ.push({a.v, d[a.v]});
           }
       }
   }
   if (d[n] == oo)
   {
       cout << -1; return ;
   }
   cout << d[n];
}
int main()
{
   ios_base::sync_with_stdio(false);
   cin.tie(nullptr);
   freopen(TASK".INP", "r", stdin);
   freopen(TASK".OUT", "w", stdout);
   int t = 1;
   bool typetest = false;
   if (typetest)
   {
      cin >> t;
   }
   for (int __ = 1; __ <= t; ++ __)
   {
      read();
      solve();
   }
}