Submission #680705

#	Time	Username	Problem	Language	Result	Execution time	Memory
680705		SanguineChameleon	Relay Marathon (NOI20_relaymarathon)	C++17	100 / 100	1761 ms	128940 KiB

RelayMarathon

// BEGIN BOILERPLATE CODE

#include <bits/stdc++.h>
using namespace std;

#ifdef KAMIRULEZ
	const bool kami_loc = true;
	const long long kami_seed = 69420;
#else
	const bool kami_loc = false;
	const long long kami_seed = chrono::steady_clock::now().time_since_epoch().count();
#endif

const string kami_fi = "kamirulez.inp";
const string kami_fo = "kamirulez.out";
mt19937_64 kami_gen(kami_seed);

long long rand_range(long long rmin, long long rmax) {
	uniform_int_distribution<long long> rdist(rmin, rmax);
	return rdist(kami_gen);
}

long double rand_real(long double rmin, long double rmax) {
	uniform_real_distribution<long double> rdist(rmin, rmax);
	return rdist(kami_gen);
}

void file_io(string fi, string fo) {
	if (fi != "" && (!kami_loc || fi == kami_fi)) {
		freopen(fi.c_str(), "r", stdin);
	}
	if (fo != "" && (!kami_loc || fo == kami_fo)) {
		freopen(fo.c_str(), "w", stdout);
	}
}

void set_up() {
	if (kami_loc) {
		file_io(kami_fi, kami_fo);
	}
	ios_base::sync_with_stdio(0);
	cin.tie(0);
}

void just_do_it();

void just_exec_it() {
	if (kami_loc) {
		auto pstart = chrono::steady_clock::now();
		just_do_it();
		auto pend = chrono::steady_clock::now();
		long long ptime = chrono::duration_cast<chrono::milliseconds>(pend - pstart).count();
		string bar(50, '=');
		cout << '\n' << bar << '\n';
		cout << "Time: " << ptime << " ms" << '\n';
	}
	else {
		just_do_it();
	}
}

int main() {
	set_up();
	just_exec_it();
	return 0;
}

// END BOILERPLATE CODE

// BEGIN MAIN CODE

const int ms = 1e5 + 20;
const int inf = 1e9 + 20;
vector<pair<int, int>> adj[ms];
int ds[ms];
int du[ms];
int dv[ms];
int h[ms];
int g[ms];
bool f[ms];
int n;

void dijk(int d[]) {
	priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> q;
	for (int i = 1; i <= n; i++) {
		if (d[i] == 0) {
			h[i] = i;
			q.push({0, i});
		}
	}
	while (!q.empty()) {
		int cd = q.top().first;
		int u = q.top().second;
		q.pop();
		if (d[u] != cd) {
			continue;
		}
		for (auto x: adj[u]) {
			int v = x.first;
			if (f[v]) {
				continue;
			}
			int w = x.second;
			if (d[u] + w < d[v]) {
				d[v] = d[u] + w;
				h[v] = h[u];
				q.push({d[v], v});
			}
		}
	}
}

bool cmp(int u, int v) {
	return dv[u] < dv[v];
}

void just_do_it() {
	//file_io("4special.inp", "4special.out");
	int m, k;
	cin >> n >> m >> k;
	for (int i = 1; i <= n; i++) {
		ds[i] = inf;
		du[i] = inf;
		dv[i] = inf;
	}
	for (int i = 0; i < m; i++) {
		int u, v, w;
		cin >> u >> v >> w;
		adj[u].push_back({v, w});
		adj[v].push_back({u, w});
	}
	for (int i = 0; i < k; i++) {
		int u;
		cin >> u;
		g[i] = u;
		ds[u] = 0;
	}
	dijk(ds);
	int mi = inf;
	int fu = -1;
	int fv = -1;
	for (int i = 1; i <= n; i++) {
		for (auto x: adj[i]) {
			int j = x.first;
			int w = x.second;
			if (h[i] != h[j]) {
				if (ds[i] + ds[j] + w < mi) {
					mi = ds[i] + ds[j] + w;
					fu = h[i];
					fv = h[j];
				}
			}
		}
	}
	du[fu] = 0;
	dijk(du);
	dv[fv] = 0;
	dijk(dv);
	sort(g, g + k, cmp);
	int res = inf;
	for (int i = 0; i < k; i++) {
		if (g[i] == fu || g[i] == fv) {
			continue;
		}
		for (int j = 0; j < k; j++) {
			if (g[j] != g[i] && g[j] != fu && g[j] != fv) {
				res = min(res, du[g[i]] + dv[g[j]]);
				break;
			}
		}
	}
	for (int i = 1; i <= n; i++) {
		ds[i] = inf;
	}
	for (int i = 0; i < k; i++) {
		ds[g[i]] = 0;
	}
	ds[fu] = inf;
	ds[fv] = inf;
	f[fu] = true;
	f[fv] = true;
	dijk(ds);
	for (int i = 1; i <= n; i++) {
		for (auto x: adj[i]) {
			int j = x.first;
			int w = x.second;
			if (h[i] != h[j]) {
				res = min(res, mi + ds[i] + ds[j] + w);
			}
		}
	}
	cout << res;
}

// END MAIN CODE

Compilation message (stderr)

RelayMarathon.cpp: In function 'void file_io(std::string, std::string)':
RelayMarathon.cpp:30:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |   freopen(fi.c_str(), "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
RelayMarathon.cpp:33:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   33 |   freopen(fo.c_str(), "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 12 / 12
• Subtask 3: 25 / 25
• Subtask 4: 58 / 58