Submission #681084

#	Time	Username	Problem	Language	Result	Execution time	Memory
681084		US3RN4M3	Aliens (IOI16_aliens)	C++17	4 / 100	1 ms	304 KiB

aliens

#include<bits/stdc++.h>
#include"aliens.h"
using namespace std;
using ll = long long;
void remove_redundancies(vector<pair<ll, ll>> & v) {
	vector<pair<ll, ll>> tmp1;
	int last = -1;
	for(auto [x, y] : v) {
		if(x == last) tmp1.pop_back();
		last = x;
		tmp1.push_back({x, y});
	}
	int n = tmp1.size();
	vector<bool> redundant(n, false);
	vector<ll> right_point(n, 0);
	vector<ll> left_point(n, 0);
	for(int i = 0; i < n; i++) {
		right_point[i] = tmp1[i].first + tmp1[i].second;
		left_point[i] = tmp1[i].first - tmp1[i].second;
	}
	for(int i = 1; i < n; i++) {
		if(right_point[i - 1] >= right_point[i]) {
			redundant[i] = true;
			right_point[i] = right_point[i - 1];
		}
	}
	for(int i = n - 2; i >= 0; i--) {
		if(left_point[i + 1] <= left_point[i]) {
			redundant[i] = true;
			left_point[i] = left_point[i + 1];
		}
	}
	v.clear();
	for(int i = 0; i < n; i++) {
		if(!redundant[i]) {
			ll x = (tmp1[i].first + tmp1[i].second) / 2;
			ll y = tmp1[i].first - x;
			v.push_back({y, x});
		}
	}
}
ll cost(pair<ll, ll> a) {
	return (a.second - a.first + 1) * (a.second - a.first + 1);
}
ll pair_cost(pair<ll, ll> a, pair<ll, ll> b) {
	if(a.second < b.first) return cost(a) + cost(b);
	else return cost(a) + cost(b) - cost({b.first, a.second});
}
ll merge_cost(pair<ll, ll> a, pair<ll, ll> b) {
	return cost({a.first, b.second}) - pair_cost(a, b);
}
void reduce(vector<pair<ll, ll>> & v) {
	vector<pair<ll, ll>> tmp;
	pair<ll, int> best = {1e18, -1};
	int n = v.size();
	for(int i = 0; i < n - 1; i++) {
		best = min(best, {merge_cost(v[i], v[i + 1]), i});
	}
	int idx = best.second;
	for(int i = 0; i < idx; i++) {
		tmp.push_back(v[i]);
	}
	tmp.push_back({v[idx].first, v[idx + 1].second});
	for(int i = idx + 2; i < n; i++) tmp.push_back(v[i]);
	swap(v, tmp);
}
long long take_photos(int n, int m, int k, std::vector<int> r, std::vector<int> c) {
	if(n > 50) return 0;
	vector<pair<ll, ll>> coords(n);
	for(int i = 0; i < n; i++) coords[i] = {r[i] + c[i], abs(r[i] - c[i])};
	sort(coords.begin(), coords.end());
	remove_redundancies(coords);
	//for(auto [x, y] : coords) cout << x << " " << y << endl;
	while(coords.size() > k) {
		reduce(coords);
	}
	ll ans = cost(coords[0]);
	for(int i = 0; i < coords.size() - 1; i++) {
		ans += pair_cost(coords[i], coords[i + 1]) - cost(coords[i]);
	}
	return ans;
}

Compilation message (stderr)

aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:74:22: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   74 |  while(coords.size() > k) {
      |        ~~~~~~~~~~~~~~^~~
aliens.cpp:78:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   78 |  for(int i = 0; i < coords.size() - 1; i++) {
      |                 ~~^~~~~~~~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 0 / 12
• Subtask 3: 0 / 9
• Subtask 4: 0 / 16
• Subtask 5: 0 / 19
• Subtask 6: 0 / 40