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Submission #853601

# Submission time Handle Problem Language Result Execution time Memory
853601 2023-09-24T17:39:01 Z mbfibat One-Way Streets (CEOI17_oneway) C++17
100 / 100
 670 ms 82548 KB 
#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> ii;
typedef tuple<int, int, int> iii;
const int N = 1e5 + 11;

int n, m;
char ans[N];
vector<int> adj[N];
map<ii, int> dir, org, cnt;

int height[N], lca[N][21];

int top = 0;
int cur[N], low[N];
map<ii, bool> is_bridge;

void dfs(int u, int p = 0) {
	cur[u] = low[u] = ++top;
	for (int v : adj[u]) {
		if (!cur[v]) {
			dfs(v, u);

			low[u] = min(low[u], low[v]);
			if (low[v] > cur[u])
				is_bridge[ii(u, v)] = is_bridge[ii(v, u)] = (cnt[ii(u, v)] == 1);
		} else if (v != p)
			low[u] = min(low[u], cur[v]);
	}
}

int id[N];
ii upd[N];
iii par[N];   
vector<iii> adj_compress[N];
void compress(int u) {
	id[u] = top;
	for (int v : adj[u]) {
		if (id[v]) {
			if (id[v] != top) {
				adj_compress[id[u]].emplace_back(id[v], u, v);
				adj_compress[id[v]].emplace_back(id[u], v, u);
			}	
			continue;
		}
		if (is_bridge[ii(u, v)]) continue;

		compress(v);
	}
}

void dfs2(int u, int p = -1) {
	cur[u] = true;
	for (int j = 1; j <= 20; j++)
		lca[u][j] = lca[lca[u][j - 1]][j - 1];

	for (auto [v, x, y] : adj_compress[u]) {
		if (v == p) continue;

		height[v] = height[u] + 1;
		lca[v][0] = u;
		par[v] = iii(u, x, y);
		dfs2(v, u);
	}
}

void upd_go(int u, int v, int edge_id) {
	if (dir[ii(u, v)]) ans[edge_id] = 'R';
	else ans[edge_id] = 'L';	
}

int cal_lca(int u, int v) {
	if (height[u] > height[v]) swap(u, v);
	for (int j = 20; j >= 0; j--)
		if (height[lca[v][j]] >= height[u])
			v = lca[v][j];
	if (u == v) return u;
	for (int j = 20; j >= 0; j--)
		if (lca[u][j] != lca[v][j]) {
			u = lca[u][j];
			v = lca[v][j];
		}
	return lca[u][0];			
}

int main(int argc, char** argv) {
	ios::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);

	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int u, v; cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);

		dir[ii(u, v)] = true;
		cnt[ii(u, v)]++; cnt[ii(v, u)]++;
		org[ii(u, v)] = org[ii(v, u)] = i;
	}

	for (int i = 1; i <= n; i++)
		if (!cur[i])
			dfs(i);

	top = 0;
	for (int i = 1; i <= n; i++)
		if (!id[i]) {
			++top;
			compress(i);
		}	

	for (int i = 1; i <= top; i++) cur[i] = 0;
	for (int i = 1; i <= top; i++)
		if (!cur[i]) {
			height[i] = 1;
			dfs2(i);
		}						
	
	for (int i = 1; i <= top; i++) upd[i] = ii(1e9, 0);
	int q; cin >> q;
	while (q--) {
		int u, v; cin >> u >> v;
		u = id[u], v = id[v];

		int p = cal_lca(u, v);

		upd[u] = min(upd[u], ii(height[p], 0));
		upd[v] = min(upd[v], ii(height[p], 1));
	}


	vector<ii> ord;
	for (int i = 1; i <= top; i++)
		ord.emplace_back(height[i], i);
	for (int i = 1; i <= m; i++)	
		ans[i] = 'B';

	sort(ord.begin(), ord.end(), greater<ii>());

	for (auto [h, u] : ord) {
		auto [cur_h, type] = upd[u];
		auto [p, x, y] = par[u];

		if (cur_h >= h) continue;

		upd[p] = min(upd[p], upd[u]);

		int edge_id = org[ii(x, y)];

		if (!type) upd_go(y, x, edge_id);
		else upd_go(x, y, edge_id);
	}

	for (int i = 1; i <= m; i++)
		cout << ans[i];
}

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 10584 KB Output is correct
2 Correct 2 ms 10588 KB Output is correct
3 Correct 5 ms 11144 KB Output is correct
4 Correct 5 ms 11096 KB Output is correct
5 Correct 4 ms 11324 KB Output is correct
6 Correct 3 ms 10844 KB Output is correct
7 Correct 4 ms 11100 KB Output is correct
8 Correct 4 ms 11100 KB Output is correct
9 Correct 4 ms 11100 KB Output is correct
10 Correct 3 ms 10844 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 10584 KB Output is correct
2 Correct 2 ms 10588 KB Output is correct
3 Correct 5 ms 11144 KB Output is correct
4 Correct 5 ms 11096 KB Output is correct
5 Correct 4 ms 11324 KB Output is correct
6 Correct 3 ms 10844 KB Output is correct
7 Correct 4 ms 11100 KB Output is correct
8 Correct 4 ms 11100 KB Output is correct
9 Correct 4 ms 11100 KB Output is correct
10 Correct 3 ms 10844 KB Output is correct
11 Correct 326 ms 47336 KB Output is correct
12 Correct 335 ms 48992 KB Output is correct
13 Correct 344 ms 52048 KB Output is correct
14 Correct 429 ms 57984 KB Output is correct
15 Correct 425 ms 61360 KB Output is correct
16 Correct 557 ms 69332 KB Output is correct
17 Correct 530 ms 72988 KB Output is correct
18 Correct 536 ms 69176 KB Output is correct
19 Correct 526 ms 75116 KB Output is correct
20 Correct 315 ms 49392 KB Output is correct
21 Correct 258 ms 47840 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 10584 KB Output is correct
2 Correct 2 ms 10588 KB Output is correct
3 Correct 5 ms 11144 KB Output is correct
4 Correct 5 ms 11096 KB Output is correct
5 Correct 4 ms 11324 KB Output is correct
6 Correct 3 ms 10844 KB Output is correct
7 Correct 4 ms 11100 KB Output is correct
8 Correct 4 ms 11100 KB Output is correct
9 Correct 4 ms 11100 KB Output is correct
10 Correct 3 ms 10844 KB Output is correct
11 Correct 326 ms 47336 KB Output is correct
12 Correct 335 ms 48992 KB Output is correct
13 Correct 344 ms 52048 KB Output is correct
14 Correct 429 ms 57984 KB Output is correct
15 Correct 425 ms 61360 KB Output is correct
16 Correct 557 ms 69332 KB Output is correct
17 Correct 530 ms 72988 KB Output is correct
18 Correct 536 ms 69176 KB Output is correct
19 Correct 526 ms 75116 KB Output is correct
20 Correct 315 ms 49392 KB Output is correct
21 Correct 258 ms 47840 KB Output is correct
22 Correct 670 ms 74936 KB Output is correct
23 Correct 632 ms 74448 KB Output is correct
24 Correct 658 ms 74304 KB Output is correct
25 Correct 667 ms 82548 KB Output is correct
26 Correct 623 ms 76424 KB Output is correct
27 Correct 636 ms 74380 KB Output is correct
28 Correct 100 ms 15020 KB Output is correct
29 Correct 335 ms 51320 KB Output is correct
30 Correct 301 ms 51168 KB Output is correct
31 Correct 356 ms 51792 KB Output is correct
32 Correct 360 ms 55872 KB Output is correct