Submission #203846

#	Time	Username	Problem	Language	Result	Execution time	Memory
203846		staniewzki	Olympic Bus (JOI20_ho_t4)	C++17	0 / 100	155 ms	2740 KiB

ho_t4

#include<bits/stdc++.h>
using namespace std;
 
ostream& operator<<(ostream &out, string str) {
	for(char c : str) out << c;
	return out;
}
 
template<class L, class R> ostream& operator<<(ostream &out, pair<L, R> p) {
	return out << "(" << p.first << ", " << p.second << ")";
}
 
template<class T> auto operator<<(ostream &out, T a) -> decltype(a.begin(), out) {
	out << "{";
	for(auto it = a.begin(); it != a.end(); it = next(it))
		out << (it != a.begin() ? ", " : "") << *it;
	return out << "}";
}
 
void dump() { cerr << "\n"; }
template<class T, class... Ts> void dump(T a, Ts... x) {
	cerr << a << ", ";
	dump(x...);
}
 
#ifdef DEBUG
#  define debug(...) cerr << "[" #__VA_ARGS__ "]: ", dump(__VA_ARGS__)
#else
#  define debug(...) false
#endif
 
#define REP(i, n) for(int i = 0; i < n; i++)
#define FOR(i, a, b) for(int i = a; i <= b; i++)
#define ST first
#define ND second
 
template<class T> int size(T && a) { return a.size(); }
 
using LL = long long;
using PII = pair<int, int>;

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);

	int n, m;
	cin >> n >> m;

	vector<int> a(m), b(m), c(m), d(m);
	vector<vector<PII>> g(n), r(n);
	REP(i, m) {
		cin >> a[i] >> b[i] >> c[i] >> d[i];
		a[i]--, b[i]--;
		g[a[i]].emplace_back(b[i], i);
		r[b[i]].emplace_back(a[i], i);
	}

	vector<bool> on_path(m);
	auto dijkstra = [&](vector<vector<PII>> &adj, int source, int banned, bool mark) {
		vector<int> dst(n, 1e9), last(n, -1);
		priority_queue<PII> Q;
		dst[source] = 0;
		Q.emplace(0, source);
		while(!Q.empty()) {
			int d, v;
			tie(d, v) = Q.top();
			Q.pop();
			if(-d != dst[v]) continue;
			for(auto &[u, e] : adj[v]) {
				if(banned == e) continue;
				if(dst[u] > dst[v] + c[e]) {
					if(mark) last[u] = e;
					dst[u] = dst[v] + c[e];
					Q.emplace(-dst[u], u);
				}
			}
		}
		REP(i, n) if(last[i] != -1)
			on_path[last[i]] = true;
		return dst;
	};

	auto norm_source = dijkstra(g, 0, -1, true);
	auto norm_sink = dijkstra(g, n - 1, -1, true);
	auto rev_source = dijkstra(r, 0, -1, false);
	auto rev_sink = dijkstra(r, n - 1, -1, false);

	auto add_edge = [&](int i) {
		g[b[i]].emplace_back(a[i], size(a));
		r[a[i]].emplace_back(b[i], size(b));
		a.emplace_back(b[i]);
		b.emplace_back(a[i]);
		c.emplace_back(c[i]);
	};

	auto pop_edge = [&](int i) {
		g[b[i]].pop_back();
		r[a[i]].pop_back();
		a.pop_back();
		b.pop_back();
		c.pop_back();
	};

	int ans = norm_source[n - 1] + norm_sink[0];

	REP(i, m) {
		if(on_path[i]) {
			add_edge(i);
			auto source = dijkstra(g, 0, i, false);
			auto sink = dijkstra(g, n - 1, i, false);
			ans = min(ans, source[n - 1] + sink[0] + d[i]);
			pop_edge(i);
		}
		else {
			int source = min(norm_source[n - 1], norm_source[b[i]] + c[i] + rev_sink[a[i]]);
			int sink = min(norm_sink[0], norm_sink[b[i]] + c[i] + rev_source[a[i]]);
			ans = min(ans, source + sink + d[i]);
		}
	}

	if(ans >= 1e9) ans = -1;
	cout << ans << "\n";
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63