Submission #796757

#	Time	Username	Problem	Language	Result	Execution time	Memory
796757		fuad27	Event Hopping (BOI22_events)	C++17	100 / 100	247 ms	44280 KiB

events

#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
const int N=200'010;
const int LG=20;
struct event {
  int s, e, idx;
};
event es[N];
struct Binary_Lifting {
  int up[N][LG];
  void add(int node, int par) {
    up[node][0]=par;
    for(int i = 1;i<LG;i++) {
      up[node][i]=up[up[node][i-1]][i-1];
    }
  }
  int get(int start, int num) {
    if(es[start].e>=num)return 1;
    int res=1;
    for(int i = LG-1;i>=0;i--) {
      if(es[up[start][i]].e<num) {
        start=up[start][i];
        res+=(1<<i);
      }
    }
    if(es[up[start][0]].e>=num)return res+1;
    return -1;
  }
};
bool operator<(const event &a, const event &b) {
  return a.e>b.e;
}
Binary_Lifting bl;
vector<int> child[N];
int out[N];
void dfs(int at) {
  for(int to:child[at]){ 
    bl.add(to,at);  
    dfs(to);
  }
}
pair<int,int> T[4*N];
void update(int at, pair<int,int> val, int tl=0, int tr=N-1, int v=1) {
  if(tl==tr) {
    T[v]=max(T[v], val);
    return;
  }
  int tm=(tl+tr)/2;
  if(at<=tm) {
    update(at, val, tl,tm,2*v);
  }
  else update(at, val, tm+1,tr,2*v+1);
  T[v]=max(T[2*v],T[2*v+1]);
}
pair<int,int> query(int l, int r, int tl=0, int tr=N-1, int v=1) {
  if(tr<l or r<tl)return {-1,-1};
  if(l<=tl and tr<=r)return T[v];
  int tm=(tl+tr)/2;
  return max(query(l,r,tl,tm,2*v), query(l,r,tm+1,tr,2*v+1));
}
int main () {
  cin.tie(0)->sync_with_stdio(0);
  int n, q;
  cin >> n >> q;
  map<int,int> cc;
  for(int i = 0;i<n;i++) {
    cin >> es[i].e >> es[i].s;
    es[i].s*=-1;
    es[i].e*=-1;
    cc[es[i].s]=1;
    cc[es[i].e]=1;
    es[i].idx=i;
  }
  vector<event> on[2*n], off[2*n];
  {
    int cnt=0;
    for(auto &i:cc) {
      i.second=cnt++;
    }
    for(int i = 0;i<n;i++) {
      es[i].s=cc[es[i].s];
      es[i].e=cc[es[i].e];
    }
  }
  for(int i = 0;i<n;i++) {
    update(es[i].s, {es[i].e, i});
  }
  for(int i = 0;i<n;i++) {
    pair<int,int> c=query(es[i].s, es[i].e);
    if(c.first>es[i].e){
      child[c.second].push_back(i);
      out[i]++;
    }
  }
  for(int i = 0;i<n;i++) {
    if(out[i]==0){
      bl.add(i,i);
      dfs(i);
    }
  }
  while(q--) {
   int s, e;
   cin >> s >> e;
   swap(s,e);
   if(es[s-1].s>es[e-1].s){
     cout << "impossible" << "\n";
     continue;
   }
   if(s==e) {
     cout << 0 << "\n";
     continue;
   }
   int res=bl.get(s-1,es[e-1].s);
   if(res>=0)cout << res << "\n";
   else cout << "impossible\n";
  }
}

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 15 / 15
• Subtask 5: 20 / 20
• Subtask 6: 30 / 30