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Submission #103830

# Submission time Handle Problem Language Result Execution time Memory
103830 2019-04-02T21:21:07 Z luciocf One-Way Streets (CEOI17_oneway) C++14
100 / 100
 309 ms 32688 KB 
#include <bits/stdc++.h>

using namespace std;

const int maxn = 1e5+10;
const int maxl = 20;

typedef pair<int, int> pii;

int n, m;

int in[maxn], low[maxn], tt;
int comp[maxn], bcc;

int pai[maxn], nivel[maxn];

int tab[maxn][maxl];

int menor[2][maxn];

int ans[maxn];

bool bridge[maxn], mark_tree[maxn];

pii edge[maxn], edgeP[maxn];

vector<pair<int, pii>> grafo[maxn], tree[maxn];

void find_bridge(int u, int ant)
{
	in[u] = low[u] = ++tt;

	for (auto pp: grafo[u])
	{
		int v = pp.first, e = pp.second.first;

		if (e == ant) continue;

		if (in[v])
		{
			low[u] = min(low[u], in[v]);
			continue;
		}

		find_bridge(v, e);

		if (low[v] > in[u]) bridge[e] = true;

		low[u] = min(low[u], low[v]);
	}
}

void mark(int u, int cc)
{
	comp[u] = cc;
	for (auto v: grafo[u])
	{
		if (comp[v.first] || bridge[v.second.first]) continue;
		mark(v.first, cc);
	}
}

void dfs(int u, int p)
{
	mark_tree[u] = true;
	for (auto pp: tree[u])
	{
		int v = pp.first, e = pp.second.first;
		if (v == p) continue;

		nivel[v] = nivel[u]+1, pai[v] = u;
		edgeP[v] = {e, pp.second.second};

		dfs(v, u);
	}
}

void build(void)
{
	memset(tab, -1, sizeof tab);

	for (int i = 1; i <= n; i++)
		tab[i][0] = pai[i];

	for (int j = 1; j < maxl; j++)
		for (int i = 1; i <= n; i++)
			if (tab[i][j-1] != -1)
				tab[i][j] = tab[tab[i][j-1]][j-1];
}

int lca(int u, int v)
{
	if (nivel[u] < nivel[v]) swap(u, v);

	for (int i = maxl-1; i >= 0; i--)
		if (nivel[u]-(1<<i) >= nivel[v])
			u = tab[u][i];

	if (u == v) return u;

	for (int i = maxl-1; i >= 0; i--)
		if (tab[u][i] != -1 && tab[v][i] != -1 && tab[u][i] != tab[v][i])
			u = tab[u][i], v = tab[v][i];

	return pai[u];
}

int solve1(int u, int p)
{
	int m = 1e9+10;
	mark_tree[u] = true;

	for (auto pp: tree[u])
	{
		int v = pp.first, e = pp.second.first;
		int direct = pp.second.second;

		if (v == p) continue;

		int x = solve1(v, u);

		if (x <= nivel[u])
		{
			if (direct) ans[e] = 0;
			else ans[e] = 1;
		}

		m = min(m, x);
	}

	return min(m, menor[1][u]);
}

int solve0(int u, int p)
{
	int m = 1e9+10;
	mark_tree[u] = true;

	for (auto pp: tree[u])
	{
		int v = pp.first, e = pp.second.first;
		int direct = pp.second.second;

		if (v == p) continue;

		int x = solve0(v, u);

		if (x <= nivel[u])
		{
			if (direct) ans[e] = 1;
			else ans[e] = 0;
		}

		m = min(m, x);
	}

	return min(m, menor[0][u]);
}

int main(void)
{
	scanf("%d %d", &n, &m);

	for (int i = 1; i <= m; i++)
	{
		int u, v;
		scanf("%d %d", &u, &v);

		edge[i] = {u, v};

		if (u != v)
		{
			grafo[u].push_back({v, {i, 1}});
			grafo[v].push_back({u, {i, 0}});
		}

		ans[i] = 2;
	}

	for (int i = 1; i <= n; i++)
		if (!in[i])
			find_bridge(i, 0);

	for (int i = 1; i <= n; i++)
		if (!comp[i])
			mark(i, ++bcc);

	for (int i = 1; i <= n; i++)
	{
		for (auto pp: grafo[i])
		{
			int v = pp.first, e = pp.second.first;
			int direct = pp.second.second;

			if (bridge[e]) tree[comp[i]].push_back({comp[v], {e, direct}});
		}
	}

	for (int i = 1; i <= bcc; i++)
	{
		menor[0][i] = menor[1][i] = 1e9+10;
		if (!mark_tree[i])
			dfs(i, 0);
	}

	build();

	int p;
	scanf("%d", &p);

	for (int i = 1; i <= p; i++)
	{
		int u, v;
		scanf("%d %d", &u, &v);
		u = comp[u], v = comp[v];
		
		int low = lca(u, v);

		menor[1][u] = min(menor[1][u], nivel[low]);
		menor[0][v] = min(menor[0][v], nivel[low]);
	}

	memset(mark_tree, 0, sizeof mark_tree);
	for (int i = 1; i <= bcc; i++)
		if (!mark_tree[i])
			solve1(i, 0);

	memset(mark_tree, 0, sizeof mark_tree);
	for (int i = 1; i <= bcc; i++)
		if (!mark_tree[i])
			solve0(i, 0);

	for (int i = 1; i <= m; i++)
	{
		if (ans[i] == 2) printf("B");
		else if (ans[i] == 1) printf("R");
		else printf("L");
	}

	printf("\n");
}

Compilation message

oneway.cpp: In function 'int main()':
oneway.cpp:162:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~~
oneway.cpp:167:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &u, &v);
   ~~~~~^~~~~~~~~~~~~~~~~
oneway.cpp:209:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &p);
  ~~~~~^~~~~~~~~~
oneway.cpp:214:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &u, &v);
   ~~~~~^~~~~~~~~~~~~~~~~

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 13 ms 12928 KB Output is correct
2 Correct 14 ms 12988 KB Output is correct
3 Correct 14 ms 13004 KB Output is correct
4 Correct 12 ms 13056 KB Output is correct
5 Correct 14 ms 13184 KB Output is correct
6 Correct 12 ms 13056 KB Output is correct
7 Correct 13 ms 13184 KB Output is correct
8 Correct 13 ms 13056 KB Output is correct
9 Correct 13 ms 13056 KB Output is correct
10 Correct 13 ms 13056 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 13 ms 12928 KB Output is correct
2 Correct 14 ms 12988 KB Output is correct
3 Correct 14 ms 13004 KB Output is correct
4 Correct 12 ms 13056 KB Output is correct
5 Correct 14 ms 13184 KB Output is correct
6 Correct 12 ms 13056 KB Output is correct
7 Correct 13 ms 13184 KB Output is correct
8 Correct 13 ms 13056 KB Output is correct
9 Correct 13 ms 13056 KB Output is correct
10 Correct 13 ms 13056 KB Output is correct
11 Correct 73 ms 20412 KB Output is correct
12 Correct 93 ms 21324 KB Output is correct
13 Correct 117 ms 22252 KB Output is correct
14 Correct 119 ms 23752 KB Output is correct
15 Correct 133 ms 24372 KB Output is correct
16 Correct 162 ms 27520 KB Output is correct
17 Correct 166 ms 28664 KB Output is correct
18 Correct 144 ms 27512 KB Output is correct
19 Correct 144 ms 29816 KB Output is correct
20 Correct 75 ms 20792 KB Output is correct
21 Correct 76 ms 20520 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 13 ms 12928 KB Output is correct
2 Correct 14 ms 12988 KB Output is correct
3 Correct 14 ms 13004 KB Output is correct
4 Correct 12 ms 13056 KB Output is correct
5 Correct 14 ms 13184 KB Output is correct
6 Correct 12 ms 13056 KB Output is correct
7 Correct 13 ms 13184 KB Output is correct
8 Correct 13 ms 13056 KB Output is correct
9 Correct 13 ms 13056 KB Output is correct
10 Correct 13 ms 13056 KB Output is correct
11 Correct 73 ms 20412 KB Output is correct
12 Correct 93 ms 21324 KB Output is correct
13 Correct 117 ms 22252 KB Output is correct
14 Correct 119 ms 23752 KB Output is correct
15 Correct 133 ms 24372 KB Output is correct
16 Correct 162 ms 27520 KB Output is correct
17 Correct 166 ms 28664 KB Output is correct
18 Correct 144 ms 27512 KB Output is correct
19 Correct 144 ms 29816 KB Output is correct
20 Correct 75 ms 20792 KB Output is correct
21 Correct 76 ms 20520 KB Output is correct
22 Correct 296 ms 29768 KB Output is correct
23 Correct 246 ms 28336 KB Output is correct
24 Correct 235 ms 28684 KB Output is correct
25 Correct 281 ms 32688 KB Output is correct
26 Correct 309 ms 29404 KB Output is correct
27 Correct 210 ms 28408 KB Output is correct
28 Correct 58 ms 18424 KB Output is correct
29 Correct 114 ms 21560 KB Output is correct
30 Correct 105 ms 21596 KB Output is correct
31 Correct 100 ms 21880 KB Output is correct
32 Correct 147 ms 25080 KB Output is correct