Submission #1021391

#	Time	Username	Problem	Language	Result	Execution time	Memory
1021391		Issa	Roller Coaster Railroad (IOI16_railroad)	C++17	100 / 100	162 ms	14416 KiB

railroad

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

const int inf = 1e9 + 100;
const ll INF = 1e18 + 100;
const int maxn = 4e5 + 100;

int n;
ll dp[1<<16][16];
int a[maxn];
int b[maxn];
vector<int> s;
int pref[maxn];
int p[maxn];

int get(int v){
	if(p[v] == v) return v;
	return p[v] = get(p[v]);
}

void join(int a, int b){
	p[get(a)] = get(b);
}

long long plan_roller_coaster(std::vector<int> s, std::vector<int> t){
	n = s.size();
	for(int i = 0; i < n; i++){
		a[i] = s[i];
		b[i] = t[i];
	}
	for(int i = 0; i < n; i++){
		s.push_back(a[i]);
		s.push_back(b[i]);
	}
	sort(s.begin(), s.end());
	s.resize(unique(s.begin(), s.end()) - s.begin());
	for(int i = 1; i <= s.size(); i++){
		p[i] = i;
	}
	for(int i = 0; i < n; i++){
		a[i] = lower_bound(s.begin(), s.end(), a[i]) - s.begin() + 1;
		b[i] = lower_bound(s.begin(), s.end(), b[i]) - s.begin() + 1;
		join(a[i], b[i]);
	}
	a[n] = s.size(); b[n] = 1;
	join(s.size(), 1);
	for(int i = 0; i <= n; i++){
		pref[a[i]]++;
		pref[b[i]]--;
	}
	ll ans = 0;
	vector<tuple<int, int, int>> v;
	for(int i = 1; i < s.size(); i++){
		pref[i] += pref[i-1];
		if(pref[i] < 0){
			join(i, i + 1);
		} else if(pref[i] > 0){
			ans += 1ll * (s[i] - s[i-1]) * pref[i];
			join(i, i + 1);
		} else{
			v.push_back({s[i] - s[i-1], i, i + 1});
		}
	}
	sort(v.begin(), v.end());
	for(auto [x, a, b]: v){
		if(get(a) != get(b)){
			ans += x;
			join(a, b);
		}
	}
	return ans;
}

Compilation message (stderr)

railroad.cpp: In function 'long long int plan_roller_coaster(std::vector<int>, std::vector<int>)':
railroad.cpp:39:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |  for(int i = 1; i <= s.size(); i++){
      |                 ~~^~~~~~~~~~~
railroad.cpp:55:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |  for(int i = 1; i < s.size(); i++){
      |                 ~~^~~~~~~~~~

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