Submission #276659

#	Time	Username	Problem	Language	Result	Execution time	Memory
276659		islingr	Olympic Bus (JOI20_ho_t4)	C++17	100 / 100	278 ms	3516 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];
bool onPath[M], vis[N];

bool dfs(int u, int t) {
	if (u == t) return true;
	vis[u] = true;
	for (int e : g[u]) {
		int v = b[e];
		if (!vis[v] && w[e] + d[v][t] == d[u][t] && dfs(v, t))
			return onPath[e] = true;
	}
	return false;
}

ll dist[N];
ll dij(int s, int t) {
	fill(dist, dist + n + 1, inf);
	fill(vis, vis + n, false);
	dist[s] = 0;
	rep(i, 0, n) {
		int u = n;
		rep(v, 0, n) if (!vis[v] && dist[v] < dist[u]) u = v;
		if (dist[u] == inf) break;
		vis[u] = true;
		for (int e : g[u]) ckmin(dist[b[e]], dist[u] + w[e]);
	}
	return dist[t];
}

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;
	fill(vis, vis + n, 0); dfs(s, t);
	fill(vis, vis + n, 0); dfs(t, s);
 
	ll ans = d[s][t] + d[t][s];
	rep(e, 0, m) {
		if (!onPath[e]) {
			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]);
			ckmin(ans, c[e] + to + fr);
		} else {
			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