Submission #1036299

#	Time	Username	Problem	Language	Result	Execution time	Memory
1036299		aymanrs	Radio Towers (IOI22_towers)	C++17	41 / 100	4082 ms	24524 KiB

towers

#include "towers.h"
#include <bits/stdc++.h>
using namespace std;
vector<int> pr, h;
const int K = 17;
vector<pair<int, int>> sp[K];
vector<int> spm[K];
vector<int> ds;
inline int msb(int x){
    return 31-__builtin_clz(x);
}
int que(int l, int r){
  int d = msb(r-l+1);
  return max(sp[d][l], sp[d][r-(1<<d)+1]).second;
}
int qum(int l, int r){
  int d = msb(r-l+1);
  return min(spm[d][l], spm[d][r-(1<<d)+1]);
}
bool sub1 = true;
int th;
void init(int N, std::vector<int> H) {
  h = H;
  pr.resize(N);
  pr[0]=0;
  auto mx = max_element(h.begin(), h.end());
  if(is_sorted(h.begin(), mx) && is_sorted(mx, h.end(), greater<int>())) {
    sub1=true;
    th = mx-h.begin();
  }
  else sub1=false;
  int l[N], r[N], p[N];
  for(int i = 0;i < K;i++) {
    sp[i].resize(N);
    spm[i].resize(N);
  }
  for(int i = 0;i < N;i++){
    l[i]=i;
    while(l[i]&&H[l[i]-1]<H[i]) l[i]=l[l[i]-1];
    sp[0][i] = {H[i], i};spm[0][i]=H[i];
  }
  for(int i = N-1;i >= 0;i--){
    r[i]=i;
    while(r[i]<N-1&&H[r[i]+1]<H[i]) r[i]=r[r[i]+1];
    if(i==th) continue;
    if(!l[i] || (r[i]<N-1&&H[l[i]-1]>H[r[i]+1])){
      p[i] = r[i]+1;
    } else {
      p[i]=l[i]-1;
    }
  }
  vector<pair<int, int>> D;
  bool mark[N] = {false};
  mark[th] = true;
  for(int i = 0;i < N;i++){
    if(i==th) continue;
    D.push_back({H[p[i]]-qum(l[i], r[i]), i});
  }
  sort(D.begin(), D.end(), greater<pair<int, int>>());
  for(auto [d, i] : D){
    mark[i] = true;
    if(mark[p[i]]) {
      mark[p[i]] = false;
    } else ds.push_back(d);
  }
  for(int k = 1;k < K;k++){
    for(int i = 0;i+(1<<k)<=N;i++){
      sp[k][i] = max(sp[k-1][i], sp[k-1][i+(1<<k-1)]);
      spm[k][i] = min(spm[k-1][i], spm[k-1][i+(1<<k-1)]);
    }
  }
  for(int i = 1;i < N-1;i++){
    pr[i]=pr[i-1];
    if(H[i] < H[i-1] && H[i] < H[i+1]) pr[i]++;
  }
}
int de;
int ans(int l, int r, int atm){
  if(l==r){
    if(h[l]<=atm) return 1;
    return 0;
  }
  int m = que(l, r);
  if(l==m) return ans(l+1, r, atm);
  if(m==r) return ans(l, r-1, atm);
  return max(ans(l, m-1, h[m]-de)+ans(m+1, r, h[m]-de), (qum(l,r) <= atm ? 1 : 0));
}
int max_towers(int L, int R, int D) {
  if(!L && R == h.size()){
    return 1+lower_bound(ds.begin(), ds.end(), D-1, greater<int>())-ds.begin();
  }
  if(sub1){
    if(L>th || R < th) return 1;
    return (h[R] <= h[th]-D && h[L] <= h[th]-D ? 2 : 1);
  }
  de = D;
  if(L+1>=R) return 1;
  if(D==1) return pr[R-1]-pr[L]+(h[L] < h[L+1])+(h[R]<h[R-1]);
  return ans(L, R, INT_MAX);
}

Compilation message (stderr)

towers.cpp: In function 'void init(int, std::vector<int>)':
towers.cpp:68:49: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
   68 |       sp[k][i] = max(sp[k-1][i], sp[k-1][i+(1<<k-1)]);
      |                                                ~^~
towers.cpp:69:52: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
   69 |       spm[k][i] = min(spm[k-1][i], spm[k-1][i+(1<<k-1)]);
      |                                                   ~^~
towers.cpp: In function 'int max_towers(int, int, int)':
towers.cpp:89:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   89 |   if(!L && R == h.size()){
      |            ~~^~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 11 / 11
• Subtask 3: 12 / 12
• Subtask 4: 14 / 14
• Subtask 5: 0 / 17
• Subtask 6: 0 / 19
• Subtask 7: 0 / 23