Submission #612964

#	Time	Username	Problem	Language	Result	Execution time	Memory
612964		Temmie	Roller Coaster Railroad (IOI16_railroad)	C++17	100 / 100	941 ms	37564 KiB

railroad

#include <bits/stdc++.h>

struct Dsu {
	
	std::unordered_map <int, int> p;
	
	inline int find(int v) {
		return p.find(v) == p.end() || v == p[v] ? (p[v] = v) : (p[v] = find(p[v]));
	}
	
	inline bool unite(int u, int v) {
		if ((u = find(u)) == (v = find(v))) {
			return false;
		}
		p[u] = v;
		return true;
	}
	
};

std::vector <std::pair <int, int>> edv;
std::vector <int> edw;
std::vector <int> edi;

int MST(Dsu& dsu) {
	long long res = 0;
	for (int x : edi) {
		res += edw[x] * dsu.unite(edv[x].first, edv[x].second);
	}
	return res;
}

long long plan_roller_coaster(std::vector <int> s, std::vector <int> t) {
	int n = s.size();
	Dsu dsu;
	std::vector <std::pair <long long, long long>> ts(n << 1);
	for (int i = 0; i < n; i++) {
		dsu.unite(s[i], t[i]);
		ts[i * 2 + 0] = { s[i], 1 };
		ts[i * 2 + 1] = { t[i], -1 };
	}
	std::sort(ts.begin(), ts.end());
	long long ans = 0, is = -1;
	for (int i = 0; i < (n << 1) - 1; i++) {
		ans += std::max(0LL, (is += ts[i].second) * (ts[i + 1].first - ts[i].first));
		if (is) {
			dsu.unite(ts[i].first, ts[i + 1].first);
		} else {
			edw.push_back(ts[i + 1].first - ts[i].first);
			edv.emplace_back(ts[i].first, ts[i + 1].first);
		}
	}
	edi.resize(edw.size());
	std::iota(edi.begin(), edi.end(), 0);
	std::sort(edi.begin(), edi.end(), [&] (int u, int v) -> bool { return edw[u] < edw[v]; });
	return ans + MST(dsu);
}

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