Submission #689952

#TimeUsernameProblemLanguageResultExecution timeMemory
689952EthanKim8683Valley (BOI19_valley)C++17
23 / 100
169 ms45748 KiB
#include<bits/stdc++.h> using namespace std; using I=int; using B=bool; using Lli=long long int; const I N=100000; const I LOGN=17; const I S=N; const I W=1e9; const Lli MAX=1e18; vector<pair<I,I>>adjs[N]; I w_arr[N-1]; I c_arr[S]; Lli lows[N]; Lli diss[N]; I deps[N]; pair<I,Lli>ancs[N][LOGN]; I bots[N-1]; I tbgs[N],teds[N]; I t=0; void dfs(I a,I p,Lli dis=0,I dep=0){ tbgs[a]=t++; diss[a]=dis,deps[a]=dep; for(auto[b,i]:adjs[a])if(b!=p){ I w=w_arr[i]; bots[i]=b; dfs(b,a,dis+w,dep+1); lows[a]=min(lows[a],lows[b]+w); } for(auto[b,w]:adjs[a])if(b!=p)ancs[b][0]={a,dis-lows[a]}; teds[a]=t; } Lli qry(I i,I j){ Lli res=diss[i]-lows[i]; for(I k=0;k<LOGN;k++)if(j>>k&1){ auto[l,d]=ancs[i][k]; i=l,res=max(res,d); } return res; } B anc(I a,I b){ return tbgs[a]<=tbgs[b]&&teds[a]>=teds[b]; } I main(){ cin.tie(0)->sync_with_stdio(0); I n,s,q,e;cin>>n>>s>>q>>e,e--; for(I i=0;i<n-1;i++){ I a,b,w;cin>>a>>b>>w,a--,b--; adjs[a].push_back({b,i}); adjs[b].push_back({a,i}); w_arr[i]=w; } for(I i=0;i<s;i++){I c;cin>>c,c_arr[i]=c-1;} fill_n(lows,n,MAX); for(I i=0;i<s;i++)lows[c_arr[i]]=0; dfs(e,e); ancs[e][0]={e,MAX}; for(I i=1;i<LOGN;i++)for(I j=0;j<n;j++){ auto[k,d1]=ancs[j][i-1];auto[l,d2]=ancs[k][i-1]; ancs[j][i]={l,max(d1,d2)}; } while(q--){ I i,r;cin>>i>>r,i--,r--; I j=bots[i]; if(!anc(j,r)){printf("escaped\n");continue;} Lli d=diss[r]-qry(r,deps[r]-deps[j]); d>(Lli)N*W?printf("oo"):printf("%lli\n",d); } }
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