Submission #276570

#	Time	Username	Problem	Language	Result	Execution time	Memory
276570		islingr	Olympic Bus (JOI20_ho_t4)	C++17	100 / 100	173 ms	2432 KiB

ho_t4

#include <bits/stdc++.h>
#include <ext/pb_ds/priority_queue.hpp>
using namespace std;

#define rep(i, a, b) for (auto i = (a); i < (b); ++i)
#define all(x...) begin(x), end(x)

using ll = long long;

template<class T> bool ckmin(T &a, const T &b) { return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }

const int N = 1 << 9, M = 1 << 16;
const ll inf = 1e18;

int n;
ll d[N][N];
int a[M], b[M], w[M], c[M];
vector<int> g[N];

using pq_t = __gnu_pbds::priority_queue<pair<ll, int>, greater<>>;
pq_t::point_iterator it[N];

ll dij(int s, int t) {
	pq_t pq;
	rep(u, 0, n) if (u != s) it[u] = pq.push({inf, u});
	it[s] = pq.push({0, s});
	while (!pq.empty()) {
		 ll dist; int u;
		tie(dist, u) = pq.top();
		pq.pop(); it[u] = nullptr;
		if (u == t) return dist;
		for (int e : g[u]) {
			int v = b[e];
			if (it[v] != nullptr) {
				dist += w[e];
				if (dist < it[v]->first) pq.modify(it[v], {dist, v});
				dist -= w[e];
			}
		}
	}
	return inf;
}

signed main() {
	cin.tie(nullptr)->sync_with_stdio(false);

	int m; cin >> n >> m;
	rep(u, 0, n) rep(v, 0, n) d[u][v] = inf;
	rep(u, 0, n) d[u][u] = 0;
	rep(e, 0, m) {
		cin >> a[e] >> b[e] >> w[e] >> c[e], --a[e], --b[e];
		ckmin(d[a[e]][b[e]], ll(w[e]));
		g[a[e]].push_back(e);
	}

	rep(w, 0, n) rep(u, 0, n) rep(v, 0, n) ckmin(d[u][v], d[u][w] + d[w][v]);

	int s = 0, t = n - 1;
	ll ans = d[s][t] + d[t][s];
	rep(e, 0, m) {
		ll to = min(d[s][t], d[s][b[e]] + w[e] + d[a[e]][t]);
		ll fr = min(d[t][s], d[t][b[e]] + w[e] + d[a[e]][s]);
		if (c[e] + to + fr < ans) {
			g[a[e]].erase(find(all(g[a[e]]), e));
			swap(a[e], b[e]);
			g[a[e]].push_back(e);
			ckmin(ans, c[e] + dij(s, t) + dij(t, s));
			g[a[e]].pop_back();
			swap(a[e], b[e]);
			g[a[e]].push_back(e);
		}
	}

	cout << (ans < inf ? ans : -1);
}

• Subtask 1: 5 / 5
• Subtask 2: 11 / 11
• Subtask 3: 21 / 21
• Subtask 4: 63 / 63