Submission #206919

#	Time	Username	Problem	Language	Result	Execution time	Memory
206919		savacska	Olympic Bus (JOI20_ho_t4)	C++14	100 / 100	144 ms	2936 KiB

ho_t4

#include <bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define x first
#define y second

using namespace std;

typedef long long ll;

const ll INF = (ll) 1e18;

vector <pair <int, int> > g[205], rev[205];
ll start1[205], finish1[205], start2[205], finish2[205], len[50005], cost[50005];
ll dist[205];
pair <int, int> back[205], forw[205], rebr[50005];
bool used[205], sf[50005], fs[50005];

void dijkstra(int n, int start, ll dist[], pair <int, int> parent[], vector <pair <int, int> > g[])
{
 	for (int i = 1; i <= n; i++) dist[i] = INF, used[i] = false, parent[i] = mp(0, 0);
 	dist[start] = 0;
 	for (int rep = 1; rep <= n; rep++)
 	{
 	 	int v = -1;
 	 	for (int i = 1; i <= n; i++)
 	 		if (!used[i] && (v == -1 || dist[v] > dist[i])) v = i;
 	 	if (dist[v] == INF) break;

 	 	used[v] = true;
 	 	for (int i = 0; i < (int) g[v].size(); i++)
 	 	{
 	 	 	int u = g[v][i].x, num = g[v][i].y;
 	 	 	if (dist[u] > dist[v] + len[num])
 	 	 		dist[u] = dist[v] + len[num], parent[u] = mp(v, num);
 	 	}
 	}
 	return;
}

ll schet(int n, int start, int finish, int num)
{
 	for (int i = 1; i <= n; i++) dist[i] = INF, used[i] = false;
 	dist[start] = 0;
 	for (int rep = 1; rep <= n; rep++)
 	{
 	 	int v = -1;
 	 	for (int i = 1; i <= n; i++)
 	 		if (!used[i] && (v == -1 || dist[v] > dist[i])) v = i;
 	 	if (dist[v] == INF) break;

 	 	used[v] = true;
 	 	for (int i = 0; i < (int) g[v].size(); i++)
 	 	{
 	 	 	int u = g[v][i].x, nm = g[v][i].y;
 	 	 	if (nm == num) continue;
 	 	 	dist[u] = min(dist[u], dist[v] + len[nm]);
 	 	}
 	 	if (v == rebr[num].y) dist[rebr[num].x] = min(dist[rebr[num].x], dist[v] + len[num]);
 	}
 	return dist[finish];
}

int main()
{
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	ios_base::sync_with_stdio(0); cin.tie(0);
	int n, m;
	cin >> n >> m;
	for (int i = 1; i <= m; i++)
	{
	 	int u, v;
	 	cin >> u >> v >> len[i] >> cost[i];
	 	rebr[i] = mp(u, v);
	 	g[u].pb(mp(v, i)), rev[v].pb(mp(u, i));
	}
	dijkstra(n, 1, start2, back, rev);
	dijkstra(n, n, finish2, forw, rev);
	dijkstra(n, 1, start1, back, g);
	dijkstra(n, n, finish1, forw, g);

	int tek = n;
	while (back[tek].y > 0)
	{
		sf[back[tek].y] = true;
		tek = back[tek].x; 	
	}
	tek = 1;
	while (forw[tek].y > 0)
	{
	 	fs[forw[tek].y] = true;
	 	tek = forw[tek].x;
	}

	ll ans = min(INF, start1[n] + finish1[1]);
	for (int i = 1; i <= m; i++)
	{
	 	ll cs1 = 0, cs2 = 0;
	 	if (sf[i]) cs1 = schet(n, 1, n, i);
	 	else cs1 = min(start1[n], start1[rebr[i].y] + len[i] + finish2[rebr[i].x]);
	 	if (fs[i]) cs2 = schet(n, n, 1, i);
	 	else cs2 = min(finish1[1], finish1[rebr[i].y] + len[i] + start2[rebr[i].x]);
	 	ans = min(ans, cs1 + cs2 + cost[i]);
	}
	if (ans != INF) cout << ans << '\n';
	else cout << "-1\n";
	return 0;
}

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