Submission #939729

#	Time	Username	Problem	Language	Result	Execution time	Memory
939729		vjudge1	One-Way Streets (CEOI17_oneway)	C++17	0 / 100	3091 ms	11432 KiB

oneway

#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>

#define ff first
#define ss second
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()

using namespace std;

int pow(int a,int b,int m){int ans=1;while(b){if(b&1){ans=(ans*a)%m;}b>>=1;a=(a*a)%m;}return ans;}
int binpow(int a,int b){int ans=1;while(b){if(b&1){ans=(ans*a);}b>>=1;a=(a*a);}return ans;}
  
const int N = 1e5 + 10;


int fup[N], h[N];
vector <int> g[N];
vector <int> gc[N];
int lead[N];
int vis[N], par[N];
int tin[N], tout[N], up[N][25], used[N];
int timer;

map <pair <int,int>, int > brid;

void dfsc(int v){
	vis[v] = 1;
	for(auto to : g[v]){
		if(vis[to] == 0 && !brid.count({v, to})){
			lead[to] = lead[v];
			dfsc(to);
		}
	}
}

void dfs2(int v, int p = 1) {
	tin[v] = ++timer;
	par[v] = p;
	up[v][0] = p;
	for (int i=1; i<=20; ++i)
		up[v][i] = up[up[v][i-1]][i-1];
	for (auto to : gc[v]) {
		if (to == p)continue;
		//cout <<p<<"->"<< v <<"->" << to << endl;
		dfs2 (to, v);
	}
	tout[v] = ++timer;
}

bool upper (int a, int b) {
	return tin[a] <= tin[b] && tout[a] >= tout[b];
}

int lca (int a, int b) {
	if (upper (a, b))  return a;
	if (upper (b, a))  return b;
	for (int i=20; i>=0; --i)
		if (! upper (up[a][i], b))
			a = up[a][i];
	return up[a][0];
}


void dfs (int v, int p = -1) {
	used[v] = true;
	tin[v] = fup[v] = timer++;
	for (size_t i=0; i<g[v].size(); ++i) {
		int to = g[v][i];
		if (to == p)  continue;
		if (used[to])
			fup[v] = min (fup[v], tin[to]);
		else {
			dfs (to, v);
			fup[v] = min (fup[v], fup[to]);
			if (fup[to] > tin[v]){
				brid[{v, to}] = 1;
				brid[{to, v}] = 1;
			}
		}
	}
}

main(){
	iostream::sync_with_stdio(false);  
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n, m;
    cin >> n >> m;
    
    vector <pair <int,int> > road;
    for(int i = 0; i < m; i++){
		int a, b;
		cin >> a >> b;
		g[a].pb(b);
		g[b].pb(a);
		road.pb({a, b});
	}
    
    for(int i = 1;  i<= n; i++){
		if(!used[i])dfs(i, i);
	}
	
	for(int i = 1; i <= n; i++){
		if(vis[i] == 0){
			lead[i] = i;
			dfsc(i);
		}	
	}
	
	for(auto x : road){
		if(brid.count(x)){
			//cout << "===" << x.ff <<" "<< x.ss <<" "<< lead[x.ff] <<" "<< lead[x.ss]<< endl;
			gc[lead[x.ff]].pb(lead[x.ss]);
			gc[lead[x.ss]].pb(lead[x.ff]);
		}
	}
	memset(used, 0, sizeof(used));
	for(int i = 1; i <= n; i++){
		if(par[i] == 0){
			dfs2(i, i);
		}
	}
	
	int p;
	cin >> p;
	map <pair <int,int>, int> mp;
	while(p--){
		int a, b;
		cin >> a >> b;
		a = lead[a];	
		b = lead[b];
		if(a == b)continue;
		int lc = lca(a, b);
		while(a != lc){
			//cout << "--"<<a << endl;
			if(par[a] == 0)return EXIT_FAILURE;
			mp[{lead[a], par[lead[a]]}] = 1;
			a = par[lead[a]];
		}
		while(b != lc){
			//cout << "---" << b <<" "<< par[b]<< endl;
			if(par[b] == 0)return EXIT_FAILURE;
			mp[{par[lead[b]], lead[b]}] = 1;
			b = par[lead[b]];
		}
	}
	for(auto x : road){
		int f = x.ff, s = x.ss;
		f = lead[f];
		s = lead[s];
		if(mp.count({f, s})){
			cout << 'R';
		}else if(mp.count({s, f})){
			cout << 'L';
		}else
			cout << 'B';
	}
}

Compilation message (stderr)

oneway.cpp:86:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   86 | main(){
      | ^~~~

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