Submission #1020337

#	Time	Username	Problem	Language	Result	Execution time	Memory
1020337		idiotcomputer	One-Way Streets (CEOI17_oneway)	C++11	0 / 100	5 ms	12380 KiB

oneway

#include <bits/stdc++.h>
using namespace std;
#define sz size
#define pb push_back
#define pii pair<int,int>
#define f first
#define s second

const int mxN = 1e5+5;
int vis[mxN];
vector<pii> adj[mxN];
int d[mxN];
int low[mxN];
char res[mxN];

set<int> st[mxN];
set<int> en[mxN];
int p[mxN];

int gpar(int a){
	if (p[a] == a) return a;
	p[a] = gpar(p[a]);
	return p[a];
}

void dfs(int c, int depth, int pidx){
	d[c] = depth;
	low[c] = depth;
	p[c] = c;

	for (pii i : adj[c]){
		if (vis[abs(i.s)]) continue;
		vis[abs(i.s)] = 1;
		if (d[i.f] != -1){ low[c] = min(low[c],low[i.f]); res[abs(i.s)] = 'B'; continue;}
		dfs(i.f,depth+1,i.s);
		low[c] = min(low[c],low[i.f]);
	}
	int a,b;
	for (pii i : adj[c]){
		if (d[i.f] < d[c]) continue;
		a = c;
		b = i.f;
		a = gpar(a);
		b = gpar(b);
		if ((int) st[a].sz() + (int) en[a].sz() < (int) st[b].sz() + (int) en[b].sz()) swap(a,b);
		for (int i : st[b]){
			if (en[a].find(i) != en[a].end()) en[a].erase(i);
			else st[a].insert(i);
		}
		for (int i : en[b]){
			if (st[a].find(i) != st[a].end()) st[a].erase(i);
			else en[a].insert(i);
		}
		p[b] = a;
	}
	if (pidx == INT_MAX) return;
//	cout << c << " " << low[c] << " " << d[c] << "\n";
	if (low[c] < d[c]) res[pidx] = 'B';
	else {
		a = gpar(c);
		if (st[a].sz() == 0 && en[a].sz() == 0) res[pidx] = 'B';
		else if (st[a].sz() == 0) {
			if (pidx > 0) res[abs(pidx)] = 'R';
			else res[abs(pidx)] = 'L';
		} else {
			if (pidx > 0) res[abs(pidx)] = 'L';
			else res[abs(pidx)] = 'R';
		}
	}
}


int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	int n,m;
	cin >> n >> m;

	int a,b;
	for (int i =0; i < m; i++){
		cin >> a >> b;
		a -= 1;
		b -= 1;
		adj[a].pb((pii) {b,i+1});
		adj[b].pb((pii) {a,-1*i-1});
	}	

	int p;
	cin >> p;
	for (int i =0; i < p; i++){
		cin >> a >> b;
		a -= 1;
		b -= 1;
		st[a].insert(i);
		en[b].insert(i);
	}

	memset(vis,0,sizeof(vis));
	for (int i = 0; i < n; i++) d[i] = -1;
	for (int i = 0; i < n; i++) if (d[i] == -1) dfs(i,0,INT_MAX);
	
	for (int i = 1; i <= m; i++) cout << res[i];
	cout << '\n';

	return 0;
}

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