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Submission #438622

# Submission time Handle Problem Language Result Execution time Memory
438622 2021-06-28T10:20:52 Z huangqr One-Way Streets (CEOI17_oneway) C++14
100 / 100
 131 ms 16416 KB 
#include<bits/stdc++.h>
using namespace std;
typedef int ll;
typedef pair<ll,ll> pl;
const ll lim=1e5+5;
ll n,m,q;
vector<char>ans;

struct UFDS{
	ll par[lim];
	UFDS(){
		for(int i=0;i<lim;i++)par[i]=i;
	}
	ll findset(ll pos){
		if(pos==par[pos])return pos;
		else return par[pos]=findset(par[pos]);
	}
	void mergeset(ll a,ll b){
		a = findset(a),b = findset(b);
		if(a!=b)par[b]=a;
	}
}ufds;

struct Edge{
	ll x,a,b,idx;//x is the other guy, a and b are original order of edge
	Edge(ll xx,ll aa,ll bb,ll ii){
		x=xx,a=aa,b=bb,idx=ii;
	}
	Edge(){}
};

struct Graph{
	vector<Edge>adjl[lim],nontree;
	ll par[lim],depth[lim];
	Edge paredge[lim];
	bool vis[lim],root[lim];
	Graph(){
		fill(vis,vis+lim,0);
		fill(root,root+lim,0);
		fill(depth,depth+lim,0);
		par[1]=1;
		depth[1]=0;
	}
	void dfs(ll pos,ll pre_idx){
		vis[pos]=1;
		for(Edge &E:adjl[pos]){
			if(E.idx==pre_idx){
				swap(E,adjl[pos].back());
				adjl[pos].pop_back();
				break;
			}
		}
		for(Edge E:adjl[pos]){
			if(!vis[E.x]){
				vis[E.x]=1;
				par[E.x]=pos;
				paredge[E.x]=E;
				depth[E.x]=depth[pos]+1;
				dfs(E.x,E.idx);
			}
			else if(pos<E.x){ //prevent duplication (each extra edge goes into nontree once only)
				nontree.push_back(E);
			}
		}
		return;
	}	
	void proc(Edge E){//marks a cycle in the tree
		ll ha=ufds.findset(E.a),hb=ufds.findset(E.b);
		while(ha!=hb){
			if(depth[ha]<depth[hb])swap(ha,hb);
			ufds.mergeset(par[ha],ha);
			ha=ufds.findset(par[ha]);
		}
	}
	void init(){//Part 1, init graph and process the nontree edges
		for(int i=1;i<=n;i++){
			if(vis[i]==0)dfs(i,-1),root[i]=1;
		}
		for(auto E:nontree)proc(E);//mark the cycles
	}
	
	//Part 2, answering the queries
	void query(ll a,ll b){
		ll ha=ufds.findset(a),hb=ufds.findset(b);
		while(ha!=hb){
			if(depth[ha]>depth[hb]){
				ll nxt=ufds.findset(par[ha]);
				ufds.mergeset(nxt,ha);
				Edge E=paredge[ha];
				assert((E.a==ha)^(E.b==ha));
				ans[E.idx]= (E.a==ha)?'R':'L';
				ha=nxt;
			}
			else{
				ll nxt=ufds.findset(par[hb]);
				ufds.mergeset(nxt,hb);
				Edge E=paredge[hb];
				assert((E.a==hb)^(E.b==hb));
				ans[E.idx]= (E.a==hb)?'L':'R';
				hb=nxt;
			}
		}
	}
};

int main(){
	ios_base::sync_with_stdio(0),cin.tie(NULL);
	cin>>n>>m;
	ans=vector<char>(m,'B');//Assume all edges can bidirectional at first
	Graph G;
	for(int i=0;i<m;i++){
		ll a,b;
		cin>>a>>b;
		if(a==b)continue;
		G.adjl[a].push_back(Edge(b,a,b,i));
		G.adjl[b].push_back(Edge(a,a,b,i));
	}
	G.init();
	cin>>q;
	while(q--){
		ll a,b;
		cin>>a>>b;
		G.query(a,b);
	}
	for(char c:ans)cout<<c;
}

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 5540 KB Output is correct
2 Correct 4 ms 5580 KB Output is correct
3 Correct 4 ms 5600 KB Output is correct
4 Correct 4 ms 5580 KB Output is correct
5 Correct 4 ms 5648 KB Output is correct
6 Correct 6 ms 5580 KB Output is correct
7 Correct 5 ms 5580 KB Output is correct
8 Correct 4 ms 5580 KB Output is correct
9 Correct 5 ms 5580 KB Output is correct
10 Correct 4 ms 5580 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 5540 KB Output is correct
2 Correct 4 ms 5580 KB Output is correct
3 Correct 4 ms 5600 KB Output is correct
4 Correct 4 ms 5580 KB Output is correct
5 Correct 4 ms 5648 KB Output is correct
6 Correct 6 ms 5580 KB Output is correct
7 Correct 5 ms 5580 KB Output is correct
8 Correct 4 ms 5580 KB Output is correct
9 Correct 5 ms 5580 KB Output is correct
10 Correct 4 ms 5580 KB Output is correct
11 Correct 78 ms 14760 KB Output is correct
12 Correct 76 ms 15420 KB Output is correct
13 Correct 83 ms 14780 KB Output is correct
14 Correct 104 ms 14416 KB Output is correct
15 Correct 118 ms 14328 KB Output is correct
16 Correct 96 ms 11976 KB Output is correct
17 Correct 85 ms 13228 KB Output is correct
18 Correct 85 ms 12136 KB Output is correct
19 Correct 74 ms 14012 KB Output is correct
20 Correct 67 ms 13812 KB Output is correct
21 Correct 62 ms 13432 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 5540 KB Output is correct
2 Correct 4 ms 5580 KB Output is correct
3 Correct 4 ms 5600 KB Output is correct
4 Correct 4 ms 5580 KB Output is correct
5 Correct 4 ms 5648 KB Output is correct
6 Correct 6 ms 5580 KB Output is correct
7 Correct 5 ms 5580 KB Output is correct
8 Correct 4 ms 5580 KB Output is correct
9 Correct 5 ms 5580 KB Output is correct
10 Correct 4 ms 5580 KB Output is correct
11 Correct 78 ms 14760 KB Output is correct
12 Correct 76 ms 15420 KB Output is correct
13 Correct 83 ms 14780 KB Output is correct
14 Correct 104 ms 14416 KB Output is correct
15 Correct 118 ms 14328 KB Output is correct
16 Correct 96 ms 11976 KB Output is correct
17 Correct 85 ms 13228 KB Output is correct
18 Correct 85 ms 12136 KB Output is correct
19 Correct 74 ms 14012 KB Output is correct
20 Correct 67 ms 13812 KB Output is correct
21 Correct 62 ms 13432 KB Output is correct
22 Correct 124 ms 14288 KB Output is correct
23 Correct 110 ms 13128 KB Output is correct
24 Correct 123 ms 13224 KB Output is correct
25 Correct 110 ms 16416 KB Output is correct
26 Correct 131 ms 14100 KB Output is correct
27 Correct 96 ms 13152 KB Output is correct
28 Correct 49 ms 12648 KB Output is correct
29 Correct 94 ms 14428 KB Output is correct
30 Correct 92 ms 14388 KB Output is correct
31 Correct 122 ms 14680 KB Output is correct
32 Correct 87 ms 15492 KB Output is correct