Submission #332152

#	Time	Username	Problem	Language	Result	Execution time	Memory
332152		quocnguyen1012	Roller Coaster Railroad (IOI16_railroad)	C++14	64 / 100	287 ms	19800 KiB

railroad

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

const int maxn = 4e5 + 5;

int lab[maxn], deg[maxn];
int n;

int findset(int u) {
  if (lab[u] == u) return u;
  return lab[u] = findset(lab[u]);
}

bool join(int u, int v) {
  u = findset(u); v = findset(v);
  if (u == v) return false;
  lab[v] = u;
  return true;
}

long long plan_roller_coaster(vector<int> s, vector<int> t) {
  vector<int> coor;
  n = s.size();
  for (int & i : s) coor.push_back(i);
  for (int & i : t) coor.push_back(i);

  sort(coor.begin(), coor.end());
  coor.erase(unique(coor.begin(), coor.end()), coor.end());
  iota(lab, lab + coor.size(), 0);

  auto compv = [&](int v) {
    return lower_bound(coor.begin(), coor.end(), v) - coor.begin();
  };
  for (int & i : s) i = compv(i);
  for (int & i : t) i = compv(i);
  for (int i = 0; i < n; ++i) {
    ++deg[s[i]];
    --deg[t[i]];
    join(s[i], t[i]);
  }
  vector<array<int, 3>> edges;
  ll ret = 0;

  int m = coor.size();

  for (int i = coor.size() - 1; i >= 1; --i) {
    edges.push_back({coor[i] - coor[i - 1], i, i - 1});
  }
  for (int i = 0; i + 1 < coor.size(); ++i) {
    deg[i + 1] += deg[i];
		ret += (coor[i + 1] - coor[i]) * max(deg[i] - 1, 0);
		if(deg[i]^1)
			join(i, i+1);
  }
  //for (int i = 0; i < coor.size(); ++i)
    //cerr << coor[i] << ' ' << deg[i] << '\n';
  sort(edges.begin(), edges.end());
  for (auto & it : edges) {
    if (join(it[1], it[2])) {
      //cerr << it[0] << ' ' << coor[it[1]] << ' ' << coor[it[2]] << '\n';
      ret += it[0];
    }
  }
  return ret;
}

#ifdef LOCAL
signed main(void) {
  ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifdef LOCAL
  freopen("A.INP", "r", stdin);
  freopen("A.OUT", "w", stdout);
#endif // LOCAL
  int n; cin >> n;
  vector<int> s(n), t(n);
  for (int & i : s) cin >> i;
  for (int & i : t) cin >> i;
  cout << plan_roller_coaster(s, t);
}
#endif // LOCAL

Compilation message (stderr)

railroad.cpp: In function 'long long int plan_roller_coaster(std::vector<int>, std::vector<int>)':
railroad.cpp:51:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   51 |   for (int i = 0; i + 1 < coor.size(); ++i) {
      |                   ~~~~~~^~~~~~~~~~~~~
railroad.cpp:46:7: warning: unused variable 'm' [-Wunused-variable]
   46 |   int m = coor.size();
      |       ^

• Subtask 1: 11 / 11
• Subtask 2: 23 / 23
• Subtask 3: 30 / 30
• Subtask 4: 0 / 36