Submission #736019

#	Time	Username	Problem	Language	Result	Execution time	Memory
736019		math_rabbit_1028	Radio Towers (IOI22_towers)	C++17	0 / 100	685 ms	5064 KiB

towers

#include "towers.h"
#include <bits/stdc++.h>
using namespace std;
 
int n;
vector<int> arr;
vector<int> upidx, downidx;
 
struct localmax {
  int idx, d, l, r;
  bool operator<(const localmax &other) const {
    return d < other.d;
  }
  void update() {
    d = arr[upidx[idx]] - max(arr[l], arr[r]);
  }
} local_value[101010];
set<localmax> local;
 
vector< pair<int, int> > Dlist;
 
void init(int N, vector<int> H) {
  n = N;
  for (int i = 0; i < N; i++) arr.push_back(H[i]);
  
  if (arr[0] < arr[1]) downidx.push_back(0);
  for (int i = 1; i < N - 1; i++) {
    if (arr[i] > arr[i - 1] && arr[i] > arr[i + 1]) upidx.push_back(i);
    if (arr[i] < arr[i - 1] && arr[i] < arr[i + 1]) downidx.push_back(i);
  }
  if (arr[N - 1] < arr[N - 2]) downidx.push_back(N - 1);
  
  for (int i = 0; i < upidx.size(); i++) {
    local_value[i] = {i, 0, downidx[i], downidx[i + 1]};
    local_value[i].update();
    local.insert(local_value[i]);
  }
 
  while (!local.empty()) {
    localmax now = *local.begin();
    Dlist.push_back({now.d, upidx[now.idx]});
    int next = (arr[now.l] < arr[now.r] ? now.l : now.r);
    local.erase(local.begin());
    if (now.idx - 1 >= 0) {
      set<localmax>::iterator iter = local.find(local_value[now.idx - 1]);
      if (iter != local.end()) {
        local.erase(iter);
        local_value[now.idx - 1].r = next;
        local_value[now.idx - 1].update();
        local.insert(local_value[now.idx - 1]);
      }
    }
    if (now.idx + 1 < upidx.size()) {      
      set<localmax>::iterator iter = local.find(local_value[now.idx + 1]);
      if (iter != local.end()) {
        local.erase(iter);
        local_value[now.idx + 1].l = next;
        local_value[now.idx + 1].update();
        local.insert(local_value[now.idx + 1]);
      }
    }
  }
 
  //for (int i = 0; i < Dlist.size(); i++) cout << Dlist[i].first << " " << Dlist[i].second << "\n";
 
}
 
int max_towers(int L, int R, int D) {
  int ans = downidx.size() - (lower_bound(Dlist.begin(), Dlist.end(), make_pair(D, 0)) - Dlist.begin());
  return ans;
}

Compilation message (stderr)

towers.cpp: In function 'void init(int, std::vector<int>)':
towers.cpp:33:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |   for (int i = 0; i < upidx.size(); i++) {
      |                   ~~^~~~~~~~~~~~~~
towers.cpp:53:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 |     if (now.idx + 1 < upidx.size()) {
      |         ~~~~~~~~~~~~^~~~~~~~~~~~~~

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