Submission #813710

#	Time	Username	Problem	Language	Result	Execution time	Memory
813710		1075508020060209tc	Cat in a tree (BOI17_catinatree)	C++14	100 / 100	347 ms	55624 KiB

catinatree

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,popcnt,sse4,abm")
#include <bits/stdc++.h>
using namespace std;
//#define int long long
#define X first
#define Y second
int n;
vector<int>e[200005];
int vis[200005];
int fa[25][200005];
int dis[25][200005];
int dph[200005];
int sbsz[200005];
int lvl[200005];
void dfssz(int nw,int pa){
sbsz[nw]=1;
for(int i=0;i<e[nw].size();i++){
    int v=e[nw][i];
    if(vis[v]||v==pa){continue;}
    dfssz(v,nw);
    sbsz[nw]+=sbsz[v];
}
}
int fincen(int nw,int pa,int tot){
for(int i=0;i<e[nw].size();i++){
    int v=e[nw][i];
    if(vis[v]||v==pa){continue;}
    int vl=fincen(v,nw,tot);
    if(vl){return vl;}
}
if(sbsz[nw]*2>=tot){
    return nw;
}return 0;
}
void dfsdph(int nw,int pa,int flv,int cfa){
dph[nw]=dph[pa]+1;
for(int i=0;i<e[nw].size();i++){
    int v=e[nw][i];
    if(v==pa||vis[v]){continue;}
    dfsdph(v,nw,flv,cfa);
}
dis[flv][nw]=dph[nw]-1;
fa[flv][nw]=cfa;
}

void decompose(int rt,int lv){
dfssz(rt,0);
int cen=fincen(rt,0,sbsz[rt]);
lvl[cen]=lv;
dfsdph(cen,0,lv,cen);
vis[cen]=1;
for(int i=0;i<e[cen].size();i++){
    int v=e[cen][i];
    if(vis[v]){continue;}
    decompose(v,lv+1);
}
}
int mnd[200005];
void upd(int v){
mnd[v]=0;
int nw=v;
for(int i=lvl[v]-1;i>=1;i--){
    nw=fa[i][v];
    int d=dis[i][v];
    mnd[nw]=min(mnd[nw],d);
}
}
int qry(int v){
int ret=mnd[v];
int nw=v;
for(int i=lvl[v]-1;i>=1;i--){
    nw=fa[i][v];
    int d=dis[i][v];
    ret=min(ret,d+mnd[nw]);
}
return ret;
}

int D;
signed main() {
cin>>n>>D;
for(int i=2;i<=n;i++){
    int a;int b;
    cin>>a;
    a++;b=i;
    e[a].push_back(b);
    e[b].push_back(a);
}
decompose(1,1);
for(int i=1;i<=n;i++){
    vis[i]=0;
}
dfsdph(1,0,0,0);
for(int i=1;i<=n;i++){
    mnd[i]=1e9;
}
vector<pair<int,int>>vc;
for(int i=1;i<=n;i++){
    vc.push_back({-dph[i],i});
}
sort(vc.begin(),vc.end());
int ans=0;
for(int i=0;i<vc.size();i++){
    int v=vc[i].second;
    if(qry(v)<D){continue;}
    ans++;
    upd(v);
}
cout<<ans<<endl;

}

Compilation message (stderr)

catinatree.cpp: In function 'void dfssz(int, int)':
catinatree.cpp:18:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   18 | for(int i=0;i<e[nw].size();i++){
      |             ~^~~~~~~~~~~~~
catinatree.cpp: In function 'int fincen(int, int, int)':
catinatree.cpp:26:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 | for(int i=0;i<e[nw].size();i++){
      |             ~^~~~~~~~~~~~~
catinatree.cpp: In function 'void dfsdph(int, int, int, int)':
catinatree.cpp:38:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 | for(int i=0;i<e[nw].size();i++){
      |             ~^~~~~~~~~~~~~
catinatree.cpp: In function 'void decompose(int, int)':
catinatree.cpp:53:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 | for(int i=0;i<e[cen].size();i++){
      |             ~^~~~~~~~~~~~~~
catinatree.cpp: In function 'int main()':
catinatree.cpp:104:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  104 | for(int i=0;i<vc.size();i++){
      |             ~^~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 40 / 40
• Subtask 3: 49 / 49