Submission #364051

#	Time	Username	Problem	Language	Result	Execution time	Memory
364051		wind_reaper	Carnival Tickets (IOI20_tickets)	C++17	16 / 100	676 ms	51448 KiB

tickets

#include "tickets.h"
#include <bits/stdc++.h>

using namespace std;

long long find_maximum(int k, vector<vector<int>> x) {
	int n = x.size(); 
	int m = x[0].size();

	vector<vector<int>> ans(n, vector<int>(m, -1));

	long long a = 0; 

	for(int i = 0; i < n; i++){
		for(int j = m-1; j >= m-k; --j){
			ans[i][j] = (m-1-j);
			a += 1LL*x[i][j];
		}
	}

	vector<array<int, 4>> b;

	for(int i = 0; i < n; i++){
		for(int j = 0; j < min(k, m/2); j++)
			for(int w = m-1; w >= max(m-k, (m+1)/2); --w)
				b.push_back({x[i][j] + x[i][w], i, j, w});
	}

	sort(b.begin(), b.end()); 
	int exchanges = 0; 
	for(auto& [red, row, mn, mx] : b){
		if(exchanges == (n*k)/2)
			break;
		if(ans[row][mx] == -1 || ans[row][mn] != -1)
			continue;
		a -= 1LL*red;
		swap(ans[row][mx], ans[row][mn]);
		exchanges++;
	}

	allocate_tickets(ans);
	return a;
}
/*
for every i, j < k exchange the i th minimum and j th maximum 
each exchange costs x[i] + x[j] ... take the first nk/2 valid exchanges

the actual order of the stuff doesnt matter
you wanna choose nk/2 pairs to remove

what happens when the stuff starts to overlap :thinkies:

...|..|...
..|.|..
*/ 

• Subtask 1: 0 / 11
• Subtask 2: 16 / 16
• Subtask 3: 0 / 14
• Subtask 4: 0 / 14
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23
• Subtask 7: 0 / 10