P43859: Weighted shortest path (1)

#include <iostream>
#include <vector>
#include <queue>
using namespace std;


typedef pair<int, int> node_distance; // First -> Weight | Second -> Node
typedef vector< vector<node_distance> > Graph;
typedef int boolean;

int dijkstra(const Graph &G, int x, int y)
{
    vector<boolean> visited(G.size(), false);
    vector<int> distance(G.size(), -1); // We consider -1 as infinite
    priority_queue< node_distance, vector<node_distance>, greater<node_distance> > pQ;
    pQ.push({0, x});
    distance[x] = 0;
    while (!pQ.empty()) {
        int current_node = pQ.top().second;
        pQ.pop();
        if (!visited[current_node]) {
            visited[current_node] = true;
            for (int i = 0; i < G[current_node].size(); ++i) {
                node_distance aux = G[current_node][i];
                if (distance[aux.second] == -1 || distance[aux.second] > distance[current_node] + aux.first) {
                    distance[aux.second] = distance[current_node] + aux.first;
                    pQ.push({distance[aux.second], aux.second});
                }
            }
        }
    }
    return distance[y];
}

int main()
{
    int n, m;
    while (cin >> n >> m) {
        Graph G(n);
        int u, v, c;
        for (int i = 0; i < m; ++i) {
            cin >> u >> v >> c;
            G[u].push_back({c, v});
        }
        int x, y;
        cin >> x >> y;
        int result = dijkstra(G, x, y);
        if (result == -1) cout << "no path from " << x << " to " << y << endl;
        else cout << result << endl;
    }
}

//JosepRivaille