Submission #1259211

#TimeUsernameProblemLanguageResultExecution timeMemory
1259211danghuyOne-Way Streets (CEOI17_oneway)C++20
100 / 100
105 ms29984 KiB
#include <bits/stdc++.h> using namespace std; #define ll int #define pb push_back const ll MAXN=1e5+5,LG=19; ll n,m,i,j,k,timedfs; int num[MAXN],low[MAXN],id[MAXN],a[MAXN],b[MAXN],mark[MAXN]; int up[MAXN][20],h[MAXN],par[MAXN],bripar[MAXN]; int goup[MAXN],godown[MAXN],addUp[MAXN],addDown[MAXN]; vector<pair<ll,ll>> adj[MAXN],adj1[MAXN]; void dfs(ll u,int pe){ num[u]=low[u]=++timedfs; for(auto e:adj[u]){ int v=e.first,idEdge=e.second; 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<int> st; st.push(u); id[u]=comp; while(!st.empty()){ int x=st.top(); st.pop(); for(auto e:adj[x]){ int v=e.first,idEdge=e.second; 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 u,ll p){ for(auto e:adj1[u]){ int v=e.first,idEdge=e.second; if(v==p) continue; h[v]=h[u]+1; par[v]=u; bripar[v]=idEdge; up[v][0]=u; for(int j=1;j<=LG;j++) up[v][j]=up[ up[v][j-1] ][j-1]; dfs1(v,u); } } int lca(int u,int v){ if(h[u]<h[v]) swap(u,v); int diff=h[u]-h[v]; for(int j=0;j<=LG;j++) if((diff>>j)&1) u=up[u][j]; if(u==v) return u; for(int j=LG;j>=0;j--){ if(up[u][j]!=up[v][j]){ u=up[u][j]; v=up[v][j]; } } return par[u]; } void dfs_acc(int u,int p){ for(auto e:adj1[u]){ int v=e.first,idEdge=e.second; if(v==p) continue; dfs_acc(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); cin>>n>>m; for(i=1;i<=m;i++){ int 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); int 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++) if(!h[i]){h[i]=0; up[i][0]=i; dfs1(i,0);} cin>>k; for(i=1;i<=k;i++){ int u,v;cin>>u>>v; u=id[u]; v=id[v]; if(u==v) continue; int w=lca(u,v); addUp[u]++; addUp[w]--; addDown[v]++; addDown[w]--; } for(i=1;i<=comp;i++) if(par[i]==0) dfs_acc(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"; }
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