Submission #872814

#	Time	Username	Problem	Language	Result	Execution time	Memory
872814		islingr	Roller Coaster Railroad (IOI16_railroad)	C++17	100 / 100	154 ms	20364 KiB

railroad

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

#define rep(i, a, b) for (auto i{a}; i < (b); ++i)
#define per(i, a, b) for (auto i{b}; i-- > (a); )
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()

template <class T> bool uin(T& a, const T& b) { return a > b ? a = b, true : false; }
template <class T> bool uax(T& a, const T& b) { return a < b ? a = b, true : false; }

using ll = long long;


#include <algorithm>
#include <cassert>
#include <vector>

namespace atcoder {

struct dsu {
  public:
    dsu() : _n(0) {}
    explicit dsu(int n) : _n(n), parent_or_size(n, -1) {}

    int merge(int a, int b) {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        int x = leader(a), y = leader(b);
        if (x == y) return x;
        if (-parent_or_size[x] < -parent_or_size[y]) std::swap(x, y);
        parent_or_size[x] += parent_or_size[y];
        parent_or_size[y] = x;
        return x;
    }

    bool same(int a, int b) {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        return leader(a) == leader(b);
    }

    int leader(int a) {
        assert(0 <= a && a < _n);
        if (parent_or_size[a] < 0) return a;
        return parent_or_size[a] = leader(parent_or_size[a]);
    }

    int size(int a) {
        assert(0 <= a && a < _n);
        return -parent_or_size[leader(a)];
    }

    std::vector<std::vector<int>> groups() {
        std::vector<int> leader_buf(_n), group_size(_n);
        for (int i = 0; i < _n; i++) {
            leader_buf[i] = leader(i);
            group_size[leader_buf[i]]++;
        }
        std::vector<std::vector<int>> result(_n);
        for (int i = 0; i < _n; i++) {
            result[i].reserve(group_size[i]);
        }
        for (int i = 0; i < _n; i++) {
            result[leader_buf[i]].push_back(i);
        }
        result.erase(
            std::remove_if(result.begin(), result.end(),
                           [&](const std::vector<int>& v) { return v.empty(); }),
            result.end());
        return result;
    }

  private:
    int _n;
    std::vector<int> parent_or_size;
};

}  // namespace atcoder


ll plan_roller_coaster(vector<int> s, vector<int> t) {
	constexpr int inf = int(1e9) + 30;
	s.push_back(inf);
	t.push_back(1);

	auto cmp = t;
	cmp.insert(cmp.end(), all(s));
	sort(all(cmp));
	cmp.erase(unique(all(cmp)), end(cmp));

	auto hsh = [&](int x) -> int {
		return lower_bound(all(cmp), x) - begin(cmp);
	};
	const int m = sz(cmp);
	const int n = sz(s);

	atcoder::dsu g(m);
	vector<ll> bal(m);
	rep(i, 0, n) {
		const auto L = hsh(s[i]);
		const auto R = hsh(t[i]);
		++bal[L];
		--bal[R];

		g.merge(L, R);
	}
	rep(i, 0, m - 1) bal[i + 1] += bal[i];
	assert(bal.back() == 0);

	vector<pair<ll, int>> mst;

	ll res = 0;
	rep(i, 0, m - 1) {
		const auto len = cmp[i + 1] - cmp[i];
		res += max(0ll, bal[i] * len);

		if (bal[i] == 0) mst.emplace_back(len, i);
		else g.merge(i, i + 1);
	}

	sort(all(mst));
	for (auto [len, i] : mst)
		if (not g.same(i, i + 1)) {
			g.merge(i, i + 1);
			res += len;
		}
	return res;
}

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