Submission #442896

#	Time	Username	Problem	Language	Result	Execution time	Memory
442896		jesus_coconut	Teleporters (IOI08_teleporters)	C++17	70 / 100	265 ms	56468 KiB

teleporters

#include <bits/stdc++.h>
#define all(a) begin(a), end(a)
#define S second
#define F first
using namespace std;

int const N = 1000005;

void countsort(vector<int> &v) {
	array<bool, N> tmp{};
	for (auto a : v) {
		tmp[a] = true;
	}
	v.clear();
	for (int i = 0; i < N; ++i) {
		if (tmp[i]) {
			v.push_back(i);
		}
	}
}

void cs2(vector<int> &v) {
	array<int, N> tmp{};
	for (auto a : v) tmp[a]++;
	v.clear();
	for (int i = N - 1; i > 0; --i) {
		while (tmp[i] > 0) {
			v.push_back(i);
			tmp[i]--;
		}
	}
}

void cc(vector<pair<int, int>> &v) {
	vector<int> tmp;
	tmp.reserve(v.size());
	for (auto &[a, b] : v) {
		tmp.push_back(a);
		tmp.push_back(b);
	}
	countsort(tmp);
	for (auto &[a, b] : v) {
		a = lower_bound(all(tmp), a) - begin(tmp);
		b = lower_bound(all(tmp), b) - begin(tmp);
	}
}

void countsort(vector<pair<int, int>> &v) {
	array<int, N> tmp{};
	tmp.fill(-1);
	for (auto &[a, b] : v) {
		tmp[a] = b;
	}
	v.clear();
	for (int i = 0; i < N; ++i) {
		if (tmp[i] != -1) {
			v.emplace_back(i, tmp[i]);
		}
	}
}

vector<bool> bio;
vector<int> len;
vector<int> nxt;
void findcyc(int ver, int l, int tar) {
	bio[ver] = true;
	if (ver == tar) {
		len.push_back(l);
		return;
	}
	findcyc(nxt[ver], l + 1, tar);
}

void solve() {
	int n, m;
	cin >> n >> m;
	bio.resize(2 * n);
	nxt.resize(2 * n);
	len.reserve(n);
	vector<pair<int, int>> v;
	v.reserve(2 * n);
	for (int i = 0; i < n; ++i) {
		int a, b;
		cin >> a >> b;
		v.emplace_back(a, b);
		v.emplace_back(b, a);
	}
	countsort(v);
	cc(v);
	for (int i = 0; i < 2 * n; ++i) {
		nxt[i] = (v[i].S + 1) % (2 * n);
	}
	for (int i = 0; i < 2 * n; ++i) {
		if (!bio[nxt[i]]) {
			findcyc(nxt[i], 1, i);
		}
	}
	int ans = len[0];
	len[0] = 0;
	cs2(len);
	int i = 0;
	for (; i < m && i < len.size(); ++i) {
		if (len[i] > 0) {
			ans += len[i] + 2;
		} else break;
	}
	int lft = m - i;
	if (lft % 2 == 1) {
		lft--;
		ans++;
	}
	ans += 2 * lft;
	cout << ans << '\n';
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	solve();

	return 0;
}

Compilation message (stderr)

teleporters.cpp: In function 'void solve()':
teleporters.cpp:102:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  102 |  for (; i < m && i < len.size(); ++i) {
      |                  ~~^~~~~~~~~~~~

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