Submission #227862

#	Time	Username	Problem	Language	Result	Execution time	Memory
227862		syy	Commuter Pass (JOI18_commuter_pass)	C++17	15 / 100	2088 ms	35352 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define FOR(i, a, b) for(ll i = (ll)a; i <= (ll)b; i++)
#define DEC(i, a, b) for(ll i = (ll)a; i >= (ll)b; i--)
typedef pair<ll, ll> pi;
typedef pair<pi, ll> pii;
#define f first
#define s second
#define pb push_back
#define all(v) v.begin(), v.end()
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)

ll n, m, s, t, u, v, a, b, c, ans = 1e17;
ll dist[4][100005]; // s, t, u, v;
vector<pi> adj[100005];
vector<ll> dag[100005], revdag[100005];
vector<pii> edges;

void dijkstra(ll source, ll id) {
	priority_queue<pi, vector<pi>, greater<pi> > pq;
	dist[id][source] = 0; pq.push(pi(0LL, source));
	while (!pq.empty()) {
		auto [d, x] = pq.top(); pq.pop();
		if (d != dist[id][x]) continue;
		for (auto it:adj[x]) {
			if (dist[id][it.f] == -1 or dist[id][it.f] > dist[id][x] + it.s) {
				dist[id][it.f] = dist[id][x] + it.s;
				pq.push(pi(dist[id][it.f], it.f));
			}
		}
	}
}

ll dfs(ll x, ll p, bool d) {
	ll best = dist[3][x];
	for (auto it: (d ? dag[x] : revdag[x])) {
		if (it == p) continue;
		best = min(best, dfs(it, x, d));
	}
	ans = min(ans, dist[2][x] + best);
	//cout << x << " " << best << "\n";
	return best;
}

int main() {
	fastio; cin >> n >> m >> s >> t >> u >> v;
	FOR(i, 1, m) {
		cin >> a >> b >> c;
		adj[a].pb(pi(b, c));
		adj[b].pb(pi(a, c));
		edges.pb(pii(pi(a, b), c));
	}
	memset(dist, -1, sizeof dist);
	dijkstra(s, 0); dijkstra(t, 1);
	dijkstra(u, 2); dijkstra(v, 3);
	for (auto it:edges) {
		a = it.f.f, b = it.f.s, c = it.s;
		if (dist[0][a] == -1 or dist[0][b] == -1 or dist[1][a] == -1 or dist[1][b] == -1) continue;
		if (dist[1][a] + dist[0][b] + c == dist[0][t]) swap(a, b);
		if (dist[0][a] + dist[1][b] + c == dist[0][t]) {
			dag[a].pb(b);
			revdag[b].pb(a);
		}
	}
	dfs(s, -1, 1); dfs(t, -1, 0);
	cout << min(ans, dist[3][u]);
}

• Subtask 1: 0 / 16
• Subtask 2: 15 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 45