Submission #1040192

#	Time	Username	Problem	Language	Result	Execution time	Memory
1040192		Soumya1	Roller Coaster Railroad (IOI16_railroad)	C++17	100 / 100	168 ms	23216 KiB

railroad

#include "railroad.h"
#include <bits/stdc++.h>
using namespace std;
const int mxN = 4e5 + 5;
int par[mxN], sz[mxN];
int find(int u) {
  return (u == par[u] ? u : par[u] = find(par[u]));  
}
bool merge(int u, int v) {
  u = find(u), v = find(v);
  if (u == v) return false;
  if (sz[u] > sz[v]) swap(u, v);
  par[u] = v;
  sz[v] += sz[u];
  return true;
}
long long plan_roller_coaster(std::vector<int> s, std::vector<int> t) {
  int n = s.size();
  vector<pair<int, int>> all;
  for (int i : s) all.push_back({i, 0});
  for (int i : t) all.push_back({i, 1});
  for (int i = 0; i < all.size(); i++) par[i] = i, sz[i] = 1;
  int cur = 0;
  long long ans = 0;
  vector<tuple<int, int, int>> edges;
  sort(all.begin(), all.end());
  for (int i = 0; i < n; i++) {
    int x = lower_bound(all.begin(), all.end(), pair<int, int> {s[i], 0}) - all.begin();
    int y = lower_bound(all.begin(), all.end(), pair<int, int> {t[i], 1}) - all.begin();
    merge(x, y);
  }
  for (int i = 0; i + 1 < all.size(); i++) {
    auto [x, t] = all[i];
    if (!t) cur++;
    else cur--;
    if (cur > 1) {
      ans += 1LL * (cur - 1) * (all[i + 1].first - all[i].first);
      merge(i, i + 1);
    } else if (cur < 1) {
      merge(i, i + 1);
    }
    edges.push_back({all[i + 1].first - all[i].first, i, i + 1});
  }
  sort(edges.begin(), edges.end());
  for (auto [w, u, v] : edges) {
    if (merge(u, v)) {
      ans += w;
    }
  }
  return ans;
}

Compilation message (stderr)

railroad.cpp: In function 'long long int plan_roller_coaster(std::vector<int>, std::vector<int>)':
railroad.cpp:22:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   22 |   for (int i = 0; i < all.size(); i++) par[i] = i, sz[i] = 1;
      |                   ~~^~~~~~~~~~~~
railroad.cpp:32:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |   for (int i = 0; i + 1 < all.size(); i++) {
      |                   ~~~~~~^~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 23 / 23
• Subtask 3: 30 / 30
• Subtask 4: 36 / 36