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Submission #103834

# Submission time Handle Problem Language Result Execution time Memory
103834 2019-04-02T22:15:39 Z luciocf One-Way Streets (CEOI17_oneway) C++14
100 / 100
 386 ms 28792 KB 
// CEOI 2017 - One-Way Streets
// Lúcio Cardoso

#include <bits/stdc++.h>

using namespace std;

const int maxn = 1e5+10;
const int maxl = 20;
const int inf = 1e9+10;

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[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 fill(int u, int cc)
{
	comp[u] = cc;

	for (auto v: grafo[u])
		if (!comp[v.first] && !bridge[v.second.first])
			fill(v.first, cc);
}

void dfs(int u, int p)
{
	mark[u] = true;
	menor[0][u] = menor[1][u] = inf;

	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;

		dfs(v, u);
	}
}

void build(void)
{
	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++)
			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] && tab[v][i] && tab[u][i] != tab[v][i])
			u = tab[u][i], v = tab[v][i];

	return pai[u];
}

int solve_up(int u, int p)
{
	int m = inf;
	mark[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 = solve_up(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 solve_down(int u, int p)
{
	int m = inf;
	mark[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 = solve_down(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);

		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])
			fill(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++)
		if (!mark[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, 0, sizeof mark);
	for (int i = 1; i <= bcc; i++)
		if (!mark[i])
			solve_up(i, 0);

	memset(mark, 0, sizeof mark);
	for (int i = 1; i <= bcc; i++)
		if (!mark[i])
			solve_down(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 'void dfs(int, int)':
oneway.cpp:71:21: warning: unused variable 'e' [-Wunused-variable]
   int v = pp.first, e = pp.second.first;
                     ^
oneway.cpp: In function 'int main()':
oneway.cpp:161:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~~
oneway.cpp:166:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &u, &v);
   ~~~~~^~~~~~~~~~~~~~~~~
oneway.cpp:204:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &p);
  ~~~~~^~~~~~~~~~
oneway.cpp:209:8: 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 6 ms 5248 KB Output is correct
2 Correct 6 ms 5120 KB Output is correct
3 Correct 7 ms 5348 KB Output is correct
4 Correct 7 ms 5376 KB Output is correct
5 Correct 8 ms 5376 KB Output is correct
6 Correct 8 ms 5248 KB Output is correct
7 Correct 7 ms 5376 KB Output is correct
8 Correct 7 ms 5376 KB Output is correct
9 Correct 6 ms 5248 KB Output is correct
10 Correct 8 ms 5248 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 5248 KB Output is correct
2 Correct 6 ms 5120 KB Output is correct
3 Correct 7 ms 5348 KB Output is correct
4 Correct 7 ms 5376 KB Output is correct
5 Correct 8 ms 5376 KB Output is correct
6 Correct 8 ms 5248 KB Output is correct
7 Correct 7 ms 5376 KB Output is correct
8 Correct 7 ms 5376 KB Output is correct
9 Correct 6 ms 5248 KB Output is correct
10 Correct 8 ms 5248 KB Output is correct
11 Correct 72 ms 12104 KB Output is correct
12 Correct 78 ms 13916 KB Output is correct
13 Correct 104 ms 16376 KB Output is correct
14 Correct 125 ms 19960 KB Output is correct
15 Correct 143 ms 21312 KB Output is correct
16 Correct 166 ms 24736 KB Output is correct
17 Correct 174 ms 25848 KB Output is correct
18 Correct 164 ms 24824 KB Output is correct
19 Correct 187 ms 27100 KB Output is correct
20 Correct 83 ms 14840 KB Output is correct
21 Correct 110 ms 14616 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 5248 KB Output is correct
2 Correct 6 ms 5120 KB Output is correct
3 Correct 7 ms 5348 KB Output is correct
4 Correct 7 ms 5376 KB Output is correct
5 Correct 8 ms 5376 KB Output is correct
6 Correct 8 ms 5248 KB Output is correct
7 Correct 7 ms 5376 KB Output is correct
8 Correct 7 ms 5376 KB Output is correct
9 Correct 6 ms 5248 KB Output is correct
10 Correct 8 ms 5248 KB Output is correct
11 Correct 72 ms 12104 KB Output is correct
12 Correct 78 ms 13916 KB Output is correct
13 Correct 104 ms 16376 KB Output is correct
14 Correct 125 ms 19960 KB Output is correct
15 Correct 143 ms 21312 KB Output is correct
16 Correct 166 ms 24736 KB Output is correct
17 Correct 174 ms 25848 KB Output is correct
18 Correct 164 ms 24824 KB Output is correct
19 Correct 187 ms 27100 KB Output is correct
20 Correct 83 ms 14840 KB Output is correct
21 Correct 110 ms 14616 KB Output is correct
22 Correct 386 ms 25936 KB Output is correct
23 Correct 254 ms 24484 KB Output is correct
24 Correct 261 ms 24824 KB Output is correct
25 Correct 328 ms 28792 KB Output is correct
26 Correct 305 ms 25560 KB Output is correct
27 Correct 274 ms 24568 KB Output is correct
28 Correct 54 ms 8568 KB Output is correct
29 Correct 102 ms 14476 KB Output is correct
30 Correct 108 ms 14712 KB Output is correct
31 Correct 107 ms 14852 KB Output is correct
32 Correct 170 ms 18824 KB Output is correct