Submission #32064

#	Time	Username	Problem	Language	Result	Execution time	Memory
32064		imeimi2000	Roller Coaster Railroad (IOI16_railroad)	C++14	30 / 100	416 ms	48732 KiB

railroad

#include "railroad.h"
#include <algorithm>

using namespace std;
typedef long long llong;
typedef pair<int, int> pi;

int n;
vector<int> comp;
int bsearch(int x) {
	int s = 0, e = comp.size() - 1, m;
	while (s < e) {
		m = (s + e) / 2;
		if (comp[m] == x) return m;
		if (comp[m] < x) s = m + 1;
		else e = m - 1;
	}
	return s;
}

int degree[400000];
int group[400000];
int par[400000];
vector<int> edge[400000];
pi mst[400000];

void dfs(int x, int s) {
	group[x] = s;
	for (int i : edge[x]) {
		if (group[i] > 0) continue;
		dfs(i, s);
	}
}

int find(int x) {
	if (par[x]) return par[x] = find(par[x]);
	return x;
}

long long plan_roller_coaster(std::vector<int> s, std::vector<int> t) {
    n = s.size();
	comp.resize(n << 1);
	for (int i = 0; i < n; ++i) {
		comp[i << 1] = s[i];
		comp[i << 1 | 1] = t[i];
	}
	sort(comp.begin(), comp.end());
	comp.erase(unique(comp.begin(), comp.end()), comp.end());
	for (int i = 0; i < n; ++i) {
		s[i] = bsearch(s[i]);
		t[i] = bsearch(t[i]);
		++degree[s[i]];
		--degree[t[i]];
		edge[s[i]].push_back(t[i]);
	}
	int need;
	llong ans = 0ll;
	for (int i = 0; i + 1 < comp.size(); ++i) {
		need = (i == 0) - degree[i];
		degree[i + 1] -= need;
		degree[i] += need;
		if (need > 0) {
			edge[i].push_back(i + 1);
		}
		else if (need < 0) {
			edge[i + 1].push_back(i);
			ans -= 1ll * need * (comp[i + 1] - comp[i]);
		}
	}
	int j = 0;
	for (int i = 0; i < comp.size(); ++i) {
		if (group[i]) continue;
		dfs(i, ++j);
	}
	for (int i = 0, j = 0; i + 1 < comp.size(); ++i) {
		if (group[i] != group[i + 1]) {
			mst[j++] = { comp[i + 1] - comp[i], i };
		}
	}
	sort(mst, mst + j);
	for (int i = 0; i < j; ++i) {
		int x = find(group[mst[i].second]), y = find(group[mst[i].second + 1]);
		if (x == y) continue;
		ans += mst[i].first;
		par[x] = y;
	}
    return ans;
}

Compilation message (stderr)

railroad.cpp: In function 'long long int plan_roller_coaster(std::vector<int>, std::vector<int>)':
railroad.cpp:58:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i + 1 < comp.size(); ++i) {
                        ^
railroad.cpp:71:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < comp.size(); ++i) {
                    ^
railroad.cpp:75:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0, j = 0; i + 1 < comp.size(); ++i) {
                               ^

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