Submission #1259199

#	Time	Username	Problem	Language	Result	Execution time	Memory
1259199		danghuy	One-Way Streets (CEOI17_oneway)	C++20	0 / 100	3092 ms	5488 KiB

oneway

#include <bits/stdc++.h>
using namespace std;
#define yes cout<<"YES"<<'\n'
#define no cout<<"NO"<<'\n'
#define si size()
#define fi first
#define se second
#define ll int
#define sr sort
#define pb push_back
const ll MAXN=1e5+5,MOD=1e6,LG=19;
ll n,m,j,k,p,i,f,dem,ans,t,l,r=1,timedfs,id[MAXN],num[MAXN],low[MAXN],mark[MAXN],a[MAXN],b[MAXN],up[MAXN][20],goup[MAXN],godown[MAXN],h[MAXN],par[MAXN],bripar[MAXN];
string s,s1;
stack<ll> scc;
vector<pair<ll,ll>> adj[MAXN],adj1[MAXN];
map<pair<ll,ll>,ll> ma;
void dfs(ll st,ll pre){
    num[st]=low[st]=++timedfs;
    scc.push(st);
    ll f=0;
    for(auto x:adj[st]){
        if(x.fi==pre)
            continue;
        if(!num[x.fi]){
            dfs(x.fi,st);
            low[st]=min(low[st],low[x.fi]);
        }
        else {  
            low[st]=min(low[st],num[x.fi]);
        }
    }
    if(low[st]==num[st]){
        while(true){
            ll v=scc.top();scc.pop();;
            id[v]=id[st];
            if(v==st)
                break;
        }
    }
}
void dfs1(ll st,ll pre){
    for(auto x:adj1[st]){
        if(x.fi==pre) continue;
        h[x.fi]=h[st]+1;
        up[x.fi][0]=st;
        par[x.fi]=st;
        bripar[x.fi]=x.se;
        for(ll j=1;j<=LG;j++)
            up[x.fi][j]=up[up[x.fi][j-1]][j-1];
        dfs1(x.fi,st);
    }
}
ll lca(ll u,ll v){
    if(h[u]!=h[v]){
        if(h[u]<h[v]) swap(u,v);
        ll cnt=h[u]-h[v];
        for(ll j=0;j<=LG;j++)
            if((cnt>>j)&1) u=up[u][j];
    }
    if(u==v)
        return u;
    for(ll j=LG;j>=0;j--)
        if(up[u][j]!=up[v][j])
            u=up[u][j],v=up[v][j];
    return up[u][0];
}
void go(ll st,ll en,ll type){
    while(st!=en){
        if(type==1)
            goup[bripar[st]]=1;
        else godown[bripar[st]]=1;
        st=par[st];
    }
}
int main(){ 
    ios::sync_with_stdio(false);    
    cin.tie(nullptr);cout.tie(0);
    // ifstream cin("baitapin.txt");
    // ofstream cout("baitapout.txt");
//    freopen("oneway.INP","r",stdin);
//    freopen("oneway.OUT","w",stdout);
    cin>>n>>m;
    ll st;
    for(i=1;i<=m;i++){
        ll u,v;
        cin>>u>>v;
        a[i]=u,b[i]=v;
        if(!ma.count({min(u,v),max(u,v)})){
            adj[u].pb({v,i});
            adj[v].pb({u,i});
        }
        ma[{min(u,v),max(u,v)}]++;
    }
    for(i=1;i<=n;i++){
        id[i]=i;
    }
    for(i=1;i<=n;i++)
        if(!num[i])
            dfs(i,i);
    unordered_set<ll> s;
    for(i=1;i<=m;i++){
        if(id[a[i]]==id[b[i]]||ma[{min(a[i],b[i]),max(a[i],b[i])}]>1)
            mark[i]=2;
        if(mark[i]!=2&&id[a[i]]!=id[b[i]]){
            adj1[id[a[i]]].pb({id[b[i]],i});
            adj1[id[b[i]]].pb({id[a[i]],i});
            s.insert(id[a[i]]);
            s.insert(id[b[i]]);
        }
    }
    for(ll x:s){
        dfs1(x,x);
    }
    cin>>k;
    for(i=1;i<=k;i++){
        ll u,v;
        cin>>u>>v;
        u=id[u],v=id[v];
        ll k=lca(u,v);
        if(k==0)
            continue;
        go(u,k,1);
        go(v,k,-1);
    }
    for(i=1;i<=m;i++){
        if(!mark[i]){
            ll f=(h[id[a[i]]]<h[id[b[i]]]?0:1);
            if(goup[i])
                mark[i]=!f;
            else if(godown[i]) mark[i]=f;
            else mark[i]=2;
        }
    }
    for(i=1;i<=m;i++){
        if(mark[i]==0)
            cout<<'R';
        else if(mark[i]==1)
            cout<<'L';
        else cout<<'B';
    }
}
/*
7 8
1 5
4 2
5 7
2 3
7 1
2 3
1 4
4 3
1
1 4
*/

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