Submission #96705

#	Time	Username	Problem	Language	Result	Execution time	Memory
96705		qkxwsm	One-Way Streets (CEOI17_oneway)	C++14	0 / 100	100 ms	92972 KiB

oneway

#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>

using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;

random_device(rd);
mt19937 rng(rd());
const long long FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();

struct custom_hash
{
	template<class T>
	unsigned long long operator()(T v) const
	{
		unsigned long long x = v;
		x += FIXED_RANDOM;
		// x += 11400714819323198485ull;
		// x = (x ^ (x >> 30)) * 13787848793156543929ull;
		x = (x ^ (x >> 27)) * 10723151780598845931ull;
		return x ^ (x >> 31);
	}
};

template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T, class U> using hash_table = gp_hash_table<T, U, custom_hash>;

template<class T>
T randomize(T mod)
{
	return (uniform_int_distribution<T>(0, mod - 1))(rng);
}
template<class T>
void readi(T &x)
{
	x = 0;
	bool negative = false;
	char c = ' ';
	while (c < '-')
	{
		c = getchar();
	}
	if (c == '-')
	{
		negative = true;
		c = getchar();
	}
	while (c >= '0')
	{
		x = x * 10 + (c - '0');
		c = getchar();
	}
	if (negative)
	{
		x = -x;
	}
}
template<class T>
void printi(T output)
{
	if (output == 0)
	{
		putchar('0');
		return;
	}
	if (output < 0)
	{
		putchar('-');
		output = -output;
	}
	int buf[20], n = 0;
	while(output)
	{
		buf[n] = ((output % 10));
		output /= 10;
		n++;
	}
	for (n--; n >= 0; n--)
	{
		putchar(buf[n] + '0');
	}
	return;
}
template<class T>
void ckmin(T &a, T b)
{
	a = min(a, b);
}
template<class T>
void ckmax(T &a, T b)
{
	a = max(a, b);
}
long long expo(long long a, long long e, long long mod)
{
	return ((e == 0) ? 1 : ((expo(a * a % mod, e >> 1, mod)) * ((e & 1) ? a : 1) % mod));
}
template<class T, class U>
void nmod(T &x, U mod)
{
	if (x >= mod) x -= mod;
}
template<class T>
T gcd(T a, T b)
{
	return (b ? gcd(b, a % b) : a);
}

#define y0 ___y0
#define y1 ___y1
#define MP make_pair
#define PB push_back
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define DBG(x) cerr << #x << " = " << (x) << endl
#define SZ(x) ((int) ((x).size()))
#define FOR(i, a, b) for (auto i = (a); i < (b); i++)
#define FORD(i, a, b) for (auto i = (a) - 1; i >= (b); i--)
#define ALL(x) (x).begin(), (x).end()

const long double PI = 4.0 * atan(1.0);
const long double EPS = 1e-9;

#define MAGIC 347
#define SINF 10007
#define CO 1000007
#define INF 1000000007
#define BIG 1000000931
#define LARGE 1696969696967ll
#define GIANT 2564008813937411ll
#define LLINF 2696969696969696969ll
#define MAXN 100013

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pdd;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<ld> vd;
typedef vector<pii> vpi;
typedef vector<pll> vpl;
typedef vector<pdd> vpd;

int N, M, K, T;
vi edge[MAXN], edge1[MAXN];
int res[MAXN], ans[MAXN];
vpi needs;
int dsu[MAXN];
int disc[MAXN], low[MAXN], parent[MAXN], depth[MAXN], st[MAXN], ft[MAXN];
int ancestor[22][MAXN];
bitset<MAXN> seen;
hash_table<int, int> eid[MAXN], bridge[MAXN];
hash_table<int, vi> dup[MAXN];
vi bcc[MAXN];
int ups[22][MAXN];
vpi edges;

int get(int u)
{
	return (u == dsu[u] ? u : dsu[u] = get(dsu[u]));
}
void merge(int u, int v)
{
	u = get(u);
	v = get(v);
	if (u == v) return;
	dsu[u] = v;
	return;
}

void dfs(int u, bool head = false)
{
	disc[u] = T;
	low[u] = T;
	seen[u] = true;
	T++;
	for (int v : edge[u])
	{
		if (v == parent[u]) continue;
		edges.PB({u, v});
		if (seen[v])
		{
			ckmin(low[u], disc[v]);
			continue;
		}
		parent[v] = u;
		dfs(v);
		ckmin(low[u], low[v]);
		if (low[v] >= disc[u] || head)
		{
			if (low[v] != disc[u])
			{
				bridge[u][v] = true;
				bridge[v][u] = true;
			}
		}
	}
}
void dfs1(int u)
{
	st[u] = T;
	ft[u] = T;
	T++;
	for (int v : edge1[u])
	{
		if (v == parent[u]) continue;
		// cerr << u << " -> " << v << endl;
		parent[v] = u;
		depth[v] = depth[u] + 1;
		dfs1(v);
		ft[u] = ft[v];
	}
}

bool insubt(int u, int v)
{
	//is v in the subtree of u?
	if (u == N) return true;
	return (st[u] <= st[v] && st[v] <= ft[u]);
}
int lca(int u, int v)
{
	//where does v need to go to?
	if (insubt(v, u)) return N;
	FORD(i, 20, 0)
	{
		if (insubt(ancestor[i][v], u))
		{
			continue;
		}
		v = ancestor[i][v];
	}
	return v;
}

void go(int u, int v)
{
	cerr << "go " << u << ' ' << v << endl;
	int w = lca(u, v);
	if (w != N)
	{
		int x = v, diff = depth[v] - depth[w] + 1;
		FORD(i, 20, 0)
		{
			if (diff & (1 << i))
			{
				// cerr << "L " << i << ' ' << x << endl;
				ups[i][x] = -1;
				x = ancestor[i][x];
			}
		}
	}
	w = lca(v, u);
	if (w != N)
	{
		int x = u, diff = depth[u] - depth[w] + 1;
		FORD(i, 20, 0)
		{
			if (diff & (1 << i))
			{
				// cerr << "W " << i << ' ' << x << endl;
				ups[i][x] = 1;
				x = ancestor[i][x];
			}
		}
	}
	//update everything on the path u -> v to be in that direction!
}


int32_t main()
{
	ios_base::sync_with_stdio(0); cin.tie(0);
	// cout << fixed << setprecision(10);
	// cerr << fixed << setprecision(10);
	// if (fopen("file.in", "r"))
	// {
	// 	freopen ("file.in", "r", stdin);
	// 	freopen ("file.out", "w", stdout);
	// }
	cin >> N >> M;
	FOR(i, 0, M)
	{
		ans[i] = -1;
	}
	FOR(i, 0, N)
	{
		dsu[i] = i;
	}
	FOR(i, 0, M)
	{
		int u, v;
		cin >> u >> v;
		u--; v--;
		if (u == v)
		{
			continue;
		}
		edge[u].PB(v);
		edge[v].PB(u);
		dup[u][v].PB(i + 1);
		dup[v][u].PB(-i - 1);
	}
	FOR(i, 0, N)
	{
		sort(ALL(edge[i]));
		edge[i].erase(unique(ALL(edge[i])), edge[i].end());
	}
	cin >> K;
	FOR(i, 0, K)
	{
		int u, v;
		cin >> u >> v;
		u--; v--;
		if (u == v) continue;
		needs.PB({u, v});
	}
	K = 0;
	FOR(i, 0, N)
	{
		if (!seen[i])
		{
			dfs(i, 1);
		}
	}
	FOR(u, 0, N)
	{
		for (int v : edge[u])
		{
			if (!bridge[u][v])
			{
				merge(u, v);
			}
		}
	}
	FOR(u, 0, N)
	{
		for (int v : edge[u])
		{
			if (bridge[u][v])
			{
				edge1[get(u)].PB(get(v));
			}
		}
	}
	// FOR(i, 0, N)
	// {
	// 	cerr << i << ":";
	// 	for (int v : edge1[i])
	// 	{
	// 		cerr << ' ' << v;
	// 	}
	// 	cerr << endl;
	// }
	FOR(i, 0, N)
	{
		parent[i] = N;
	}
	T = 0;
	FOR(i, 0, N)
	{
		if (get(i) == i && parent[i] == N)
		{
			dfs1(i);
		}
	}
	FOR(i, 0, N)
	{
		ancestor[0][i] = parent[i];
		// cerr << parent[i] << ' ';
	}
	// cerr << endl;
	FOR(i, 0, 21)
	{
		ancestor[i][N] = N;
	}
	FOR(i, 1, 21)
	{
		FOR(j, 0, N)
		{
			ancestor[i][j] = ancestor[i - 1][ancestor[i - 1][j]];
		}
	}
	for (pii p : needs)
	{
		int u = get(p.fi), v = get(p.se);
		if (u == v) continue;
		go(u, v);
		// cerr << "go " << u << ' ' << v << endl;
	}
	FORD(i, 20, 1)
	{
		FOR(j, 0, N)
		{
			if (ups[i][j])
			{
				ups[i - 1][j] = ups[i][j];
				ups[i - 1][ancestor[i - 1][j]] = ups[i][j];
			}
		}
	}
	FOR(i, 0, N)
	{
		res[i] = -1;
		if (ups[0][i] == -1)
		{
			res[i] = 0;
		}
		if (ups[0][i] == 1)
		{
			res[i] = 1;
		}
		cerr << res[i] << endl;
	}
	FOR(i, 0, N)
	{
		for (auto p : dup[i])
		{
			if (SZ(p.se) > 1) continue;
			int u = get(i), v = get(p.fi), ed = p.se[0];
			if (ed < 0) continue;
			ed--;
			if (u == v) continue;
			// cerr << u << " -> " << v << endl;
			if (parent[v] == u)
			{
				ans[ed] = (res[v] == -1 ? -1 : res[v]);
			}
			else
			{
				ans[ed] = (res[u] == -1 ? -1 : res[u] ^ 1);
			}
		}
	}
	FOR(i, 0, M)
	{
		if (ans[i] == -1)
		{
			cout << 'B';
		}
		if (ans[i] == 0)
		{
			cout << 'R';
		}
		if (ans[i] == 1)
		{
			cout << 'L';
		}
	}
	cout << '\n';
	// cerr << "time elapsed = " << (clock() / (CLOCKS_PER_SEC / 1000)) << " ms" << endl;
	return 0;
}
/* READ READ READ
* int overflow, maxn too small, special cases (n=1?, two distinct?), cin.tie() interactive
* reread the problem, try small cases
* note down possible sources of error as you go
* do smth instead of nothing
*/

• Subtask 1: 0 / 30
• Subtask 2: 0 / 30
• Subtask 3: 0 / 40