Submission #767937

#	Time	Username	Problem	Language	Result	Execution time	Memory
767937		SanguineChameleon	Roller Coaster Railroad (IOI16_railroad)	C++17	100 / 100	133 ms	18276 KiB

railroad

#include "railroad.h"
#include <bits/stdc++.h>
using namespace std;

const int inf = 1e9 + 20;
const int maxn = 2e5 + 20;
pair<int, int> events[maxn * 2];
pair<int, int> len[maxn * 2];
int sum[maxn * 2];
int par[maxn * 2];
int depth[maxn * 2];

int root(int u) {
	if (!par[u]) {
		return u;
	}
	else {
		return par[u] = root(par[u]);
	}
}

bool update(int u, int v) {
	int ru = root(u);
	int rv = root(v);
	if (ru == rv) {
		return false;
	}
	if (depth[ru] > depth[rv]) {
		swap(ru, rv);
	}
	par[ru] = rv;
	if (depth[ru] == depth[rv]) {
		depth[rv]++;
	}
	return true;
}

long long plan_roller_coaster(vector<int> s, vector<int> t) {
	s.push_back(inf);
	t.push_back(1);
	int n = s.size();
	for (int i = 1; i <= n; i++) {
		events[i * 2 - 1] = make_pair(s[i - 1], i);
		events[i * 2] = make_pair(t[i - 1], -i);
	}
	s.resize(n + 1);
	t.resize(n + 1);
	sort(events + 1, events + n * 2 + 1);
	int cnt = 0;
	for (int i = 1; i <= n * 2; i++) {
		if (events[i].first != events[i - 1].first) {
			len[cnt] = make_pair(events[i].first - events[i - 1].first, cnt);
			cnt++;
		}
		int id = events[i].second;
		if (id > 0) {
			s[id] = cnt;
		}
		else {
			t[-id] = cnt;
		}
	}
	for (int i = 1; i <= n; i++) {
		update(s[i], t[i]);
		sum[s[i]]++;
		sum[t[i]]--;
	}
	long long res = 0;
	for (int i = 1; i <= cnt - 1; i++) {
		sum[i] += sum[i - 1];
		if (sum[i] > 0) {
			res += 1LL * len[i].first * sum[i];
		}
		if (sum[i]) {
			update(i, i + 1);
		}
	}
	sort(len + 1, len + cnt);
	for (int i = 1; i <= cnt - 1; i++) {
		if (update(len[i].second, len[i].second + 1)) {
			res += len[i].first;
		}
	}
	return res;
}

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