Submission #434606

#	Time	Username	Problem	Language	Result	Execution time	Memory
434606		frodakcin	Carnival Tickets (IOI20_tickets)	C++17	100 / 100	742 ms	83988 KiB

tickets

#include "tickets.h"
#include <cassert>
#include <vector>
#include <numeric>
#include <algorithm>
#include <functional>

using ll = long long;

struct delta
{
	public:
		int i, v;
		bool operator > (const delta& o) const {return v > o.v;}
};

long long find_maximum(int K, std::vector<std::vector<int>> x) {
	int N = x.size();
	int M = x[0].size();

	std::vector<std::vector<int>> answer(N, std::vector<int>(M, -1));
	ll ans=0;
	for(int i=0;i<N;++i)
		for(int j=0;j<K;++j)
			ans -= x[i][j];

	std::vector<int> u(N, 0);
	std::vector<delta> gains;
	for(int i=0;i<N;++i)
		for(int j=0;j<K;++j)
			gains.push_back({i, x[i][M-j-1]+x[i][K-j-1]});
	std::nth_element(gains.begin(), gains.begin()+(N*K/2), gains.end(), std::greater<delta>());

	for(int i=0;i<N*K/2;++i)
		++u[gains[i].i], ans += gains[i].v; // u = how many R we use

	std::vector<int> L(N, 0), R(N, M), ord(N);
	std::iota(ord.begin(), ord.end(), 0);
	for(int i=0;i<K;++i)
	{
		std::nth_element(ord.begin(), ord.begin()+N/2, ord.end(), [&](int x, int y){return u[x]<u[y];});
		for(int j=0;j<N/2;++j)
			answer[ord[j]][L[ord[j]]++]=i;
		for(int j=N/2;j<N;++j)
			answer[ord[j]][--R[ord[j]]]=i, --u[ord[j]];
	}

	for(int i=0;i<N;++i)
		assert(u[i] == 0);
	ll ans2=0;
	for(int i=0;i<N;++i)
	{
		for(int j=0;j<L[i];++j)
			ans2 -= x[i][j];
		for(int j=R[i];j<M;++j)
			ans2 += x[i][j];
	}
	assert(ans == ans2);

	allocate_tickets(answer);
	return ans;
}

• Subtask 1: 11 / 11
• Subtask 2: 16 / 16
• Subtask 3: 14 / 14
• Subtask 4: 14 / 14
• Subtask 5: 12 / 12
• Subtask 6: 23 / 23
• Subtask 7: 10 / 10