VMSS '15 #4 - Frank and Roads

    1#include <bits/stdc++.h>
    2using namespace std;
    3typedef long long ll;
    4const int inf = 1e9;
    5const long long INF = 1e17; //❄️
    6int main() {
    7    ios::sync_with_stdio(0); cin.tie(0); 
    8    int t, n, m, g; cin >> t >> n >> m >> g;
    9    unordered_set<int> d;
    10    for (int i = 0; i < g; i++) {
    11        int x; cin >> x;
    12        d.insert(x);
    13    }
    14    vector<vector<pair<int, int>>> adj(n + 1);
    15    for (int i = 0; i < m; i++) {
    16        int u, v, w; cin >> u >> v >> w;
    17        adj[u].emplace_back(w, v);
    18    }
    19    vector<int> dist(n + 1, inf);
    20    dist[0] = 0;
    21    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
    22    pq.push({0, 0});
    23    while (!pq.empty()) {
    24        auto[w, u] = pq.top(); pq.pop();
    25        if (w > dist[u]) continue;
    26        for (auto[wt, v] : adj[u]) {
    27            if (dist[v] > wt + w) {
    28                dist[v] = wt + w;
    29                pq.push({dist[v], v});
    30            }
    31        }
    32    }
    33    int ans = 0;
    34    for (int i = 1; i <= n; i++) {
    35        if (d.count(i) && dist[i] <= t) ans++;
    36    }
    37    cout << ans << '\n';
    38    return 0;
    39}