Submission #1259225

#	Time	Username	Problem	Language	Result	Execution time	Memory
1259225		danghuy	One-Way Streets (CEOI17_oneway)	C++20	100 / 100	103 ms	30076 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;
ll id[MAXN],num[MAXN],low[MAXN],mark[MAXN],a[MAXN],b[MAXN],up[MAXN][20],h[MAXN],par[MAXN],bripar[MAXN];
ll addUp[MAXN],addDown[MAXN];
vector<pair<ll,ll>> adj[MAXN],adj1[MAXN];

void dfs(ll u,ll pe){
    num[u]=low[u]=++timedfs;
    for(auto e:adj[u]){
        ll v=e.fi, idEdge=e.se;
        if(idEdge==pe) continue;
        if(!num[v]){
            dfs(v,idEdge);
            low[u]=min(low[u],low[v]);
        }else low[u]=min(low[u],num[v]);
    }
}

void dfs_comp(ll u,ll comp){
    stack<ll> st; st.push(u); id[u]=comp;
    while(!st.empty()){
        ll x=st.top(); st.pop();
        for(auto e:adj[x]){
            ll v=e.fi;
            if(id[v]) continue;
            bool isBridge=0;
            if(num[x]<num[v]&&low[v]>num[x]) isBridge=1;
            if(num[v]<num[x]&&low[x]>num[v]) isBridge=1;
            if(isBridge) continue;
            id[v]=comp; st.push(v);
        }
    }
}

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]) 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(int u,int p){ 
    for(auto e:adj1[u]){
        int v=e.fi,idEdge=e.se;
        if(v==p) continue;
        go(v,u);
        addUp[u]+=addUp[v];
        addDown[u]+=addDown[v];
        int f=(h[ id[a[idEdge]] ]<h[ id[b[idEdge]] ]?0:1);
        if(addUp[v]>0 && addDown[v]==0) mark[idEdge]=!f;
        else if(addDown[v]>0 && addUp[v]==0) mark[idEdge]=f;
        else mark[idEdge]=2;
    }
}

int main(){ 
    ios::sync_with_stdio(false);    
    cin.tie(nullptr);cout.tie(0);
    cin>>n>>m;
    for(i=1;i<=m;i++){
        ll u,v; cin>>u>>v;
        a[i]=u; b[i]=v;
        adj[u].pb({v,i});
        adj[v].pb({u,i});
    }
    for(i=1;i<=n;i++) if(!num[i]) dfs(i,0);
    ll comp=0;
    for(i=1;i<=n;i++) if(!id[i]) dfs_comp(i,++comp);
    for(i=1;i<=m;i++){
        if(id[a[i]]==id[b[i]]) mark[i]=2;
        else{
            bool isBridge=0;
            if(num[a[i]]<num[b[i]]&&low[b[i]]>num[a[i]]) isBridge=1;
            if(num[b[i]]<num[a[i]]&&low[a[i]]>num[b[i]]) isBridge=1;
            if(isBridge){
                adj1[id[a[i]]].pb({id[b[i]],i});
                adj1[id[b[i]]].pb({id[a[i]],i});
            }else mark[i]=2;
        }
    }
    for(i=1;i<=comp;i++){
        h[i]=0; par[i]=0; bripar[i]=0; addUp[i]=addDown[i]=0;
        for(j=0;j<=LG;j++) up[i][j]=0;
    }
    for(i=1;i<=comp;i++){
        if(up[i][0]==0){
            up[i][0]=i;
            dfs1(i,i);
        }
    }
    cin>>k;
    for(i=1;i<=k;i++){
        ll u,v; cin>>u>>v;
        u=id[u]; v=id[v];
        if(u==v) continue;
        ll w=lca(u,v);
        addUp[u]++; addUp[w]--;
        addDown[v]++; addDown[w]--;
    }
    for(i=1;i<=comp;i++) if(par[i]==0) go(i,0);
    for(i=1;i<=m;i++){
        if(mark[i]==0) cout<<'R';
        else if(mark[i]==1) cout<<'L';
        else cout<<'B';
    }
    cout<<"\n";
    return 0;
}

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