Submission #570776

#	Time	Username	Problem	Language	Result	Execution time	Memory
570776		BackNoob	One-Way Streets (CEOI17_oneway)	C++14	0 / 100	23 ms	42680 KiB

oneway

#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define endl '\n'
#define MASK(i) (1LL << (i))
#define ull unsigned long long
#define ld long double
#define pb push_back
#define all(x) (x).begin() , (x).end()
#define BIT(x , i) ((x >> (i)) & 1) 
#define TASK "task"
#define sz(s) (int) (s).size()
 
using namespace std;
const int mxN = 3e5 + 227;
const int inf = 1e9 + 277;
const int mod = 24211007;
const ll infll = 1e18 + 7;
const int base = 307;
const int LOG = 20;
 
template <typename T1, typename T2> bool minimize(T1 &a, T2 b) {
	if (a > b) {a = b; return true;} return false;
}
template <typename T1, typename T2> bool maximize(T1 &a, T2 b) {
	if (a < b) {a = b; return true;} return false;
}
 
struct DSU{
	int n;
	vector<int> lab;
	DSU(){}
	DSU(int _n) {
		n = _n;
		lab.resize(n + 7, -1);
	}
 
	int root(int u) {return lab[u] < 0 ? u : lab[u] = root(lab[u]);}	
	bool union_root(int u, int v)
	{
		u = root(u);
		v = root(v);
		if(u == v) return false;
		if(lab[u] > lab[v]) swap(lab[u], lab[v]);
		lab[u] += lab[v];
		lab[v] = u;
		return true;
	}
} dsu;
 
 
 
int n;
int m;
vector<pair<int, int>> g[mxN];
vector<pair<int, int>> rg[mxN];
vector<pair<int, int>> adj[mxN];
vector<pair<int, int >> tree[mxN];
int p[mxN];
int depth[mxN];
int idx[mxN];
int low[mxN];
int num[mxN];
int ans[mxN];
int sub[mxN];
int id[mxN];
bool bridge[mxN];
bool vis[mxN];
bool mark[mxN];
int cur[mxN];
int timer = 0;
map<int, int> mp[mxN];
pair<int, int> edges[mxN];
multiset<int> ms1, ms2;
 
 
void dfs(int u, int par)
{
	low[u] = num[u] = ++timer;
	for(auto it : adj[u]) {
		int v = it.fi;
		int idx = it.se;
		if(v == par) continue;
		if(num[v] == 0) {
			dfs(v, u);
			low[u] = min(low[u], low[v]);
			if(low[v] == num[v] && mp[u][v] == 1) {
				bridge[idx] = true;
			}
		}
		else low[u] = min(low[u], num[v]);
	}
}
 
void dfs_tree(int u, int par)
{
	id[u] = ++timer;
	for(auto it: tree[u]) {
		int v = it.fi;
		int idx = it.se;
		if(v == par) continue;
		dfs_tree(v, u);
		sub[u] += sub[v];
	}
}

void dfs_tree1(int u, int par)
{
	for(auto it : tree[u]) {
		int v = it.fi;
		int idx = it.se;
		if(v == par) continue;
		dfs_tree1(v, u);
 		cur[u] += cur[v];
		if(bridge[idx] == true && cur[v] > 0) {
			if(edges[idx].fi == u) {
				ans[idx] = 0;
			}
			else {
				ans[idx] = 1;
			}
		}
	}
 
 
	for(auto it : g[u]) {
		int v = it.fi;
		int lef = id[u];
		int rig = lef + sub[u] - 1;
		if(lef <= id[v] && id[v] <= rig) {

		}
		else ++cur[u];
	}
 
	for(auto it : g[u]) {
		int v = it.fi;
		int lef = id[u];
		int rig = lef + sub[u] - 1;
		if(lef <= id[v] && id[v] <= rig) --cur[u];
	}
}
 
void dfs_tree2(int u, int par)
{
	for(auto it : tree[u]) {
		int v = it.fi;
		int idx = it.se;
		if(v == par) continue;
		dfs_tree2(v, u);
 		cur[u] += cur[v];
		if(bridge[idx] == true && cur[v] > 0) {
			if(edges[idx].fi == u) {
				ans[idx] = 1;
			}
			else {
				ans[idx] = 0;
			}
		}
	}
 
	for(auto it : rg[u]) {
		int v = it.fi;
		int lef = id[u];
		int rig = lef + sub[u] - 1;
		if(lef <= id[v] && id[v] <= rig) {

		}
		else ++cur[u];
	}
 
	for(auto it : g[u]) {
		int v = it.fi;
		int lef = id[u];
		int rig = lef + sub[u] - 1;
		if(lef <= id[v] && id[v] <= rig) --cur[u];
	}
}
 
 
void solve()
{	
	cin >> n >> m;
	dsu = DSU(n);
	for(int i = 1; i <= m; i++) {
		int u, v;
		cin >> u >> v;
		if(dsu.union_root(u, v) == true) {
			tree[u].pb({v, i});
			tree[v].pb({u, i});
			// cout << u << ' ' << v << endl;
		}
		adj[u].pb({v, i});
		adj[v].pb({u, i});
		mp[u][v]++;
		mp[v][u]++;
		edges[i] = {u, v};
	} 
 
	int q;
	cin >> q;
	for(int i = 1; i <= q; i++) {
		int u, v;
		cin >> u >> v;
 
		g[u].pb({v, i});
		rg[v].pb({u, i});
	}
 
	dfs(1, -1);
 
	for(int i = 1; i <= m; i++) ans[i] = 2;
	for(int i = 1; i <= m; i++) if(bridge[i] == false) ans[i] = 2;
 	
 	dfs_tree(1, -1);
	dfs_tree1(1, -1);
 	for(int i = 1; i <= n; i++) cur[i] = 0;
 	dfs_tree2(1, -1);

	for(int i = 1; i <= m; i++) {
		if(ans[i] == 0) cout << "L";
		if(ans[i] == 1) cout << "R";
		if(ans[i] == 2) cout << "B";
	}
 
 	cout << endl;
}
 
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    //freopen(TASK".in" , "r" , stdin);
    //freopen(TASK".out" , "w" , stdout);
	
    int tc = 1;
    // cin >> tc;
    while(tc--) {
    	solve();
    }
    return 0;
}

Compilation message (stderr)

oneway.cpp: In function 'void dfs_tree(int, int)':
oneway.cpp:101:7: warning: unused variable 'idx' [-Wunused-variable]
  101 |   int idx = it.se;
      |       ^~~

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