Submission #743665

#	Time	Username	Problem	Language	Result	Execution time	Memory
743665		ethening	Let's Win the Election (JOI22_ho_t3)	C++17	100 / 100	521 ms	4784 KiB

Main

#include "bits/stdc++.h"
#include <functional>
#include <iomanip>
#include <vector>
using namespace std;
using ll = long long;
using pii = pair<int, int>;

int main() {
	cin.tie(0)->sync_with_stdio(0);
	int n, k;
	cin >> n >> k;
	vector<pii> pl(n + 5);
	for (int i = 1; i <= n; i++) {
		cin >> pl[i].first >> pl[i].second;
		if (pl[i].second == -1) pl[i].second = 1e9;
	}
	sort(pl.begin() + 1, pl.begin() + n + 1, [](pii& u, pii& v) {
		if (u.second == v.second) return u.first < v.first;
		else return u.second < v.second;
	});

	// suffix[i][j] = min time cost to get j region in [i, n]
	vector<vector<ll>> suffix(n + 5, vector<ll>(k + 5, 1e9));
	for (int i = n; i >= 1; i--) {
		for (int j = 0; j <= k; j++) {
			if (j > n - i + 1) break; // j > no. of region in [i, n]
			if (i == n) {
				if (j == 0) suffix[i][j] = 0;
				else if (j == 1) suffix[i][j] = pl[i].first;
			}
			else {
				suffix[i][j] = suffix[i + 1][j];
				if (j > 0) suffix[i][j] = min(suffix[i][j], suffix[i + 1][j - 1] + pl[i].first);
			}
		}
	}

	double ans = 1e16;
	for (int coop = 0; coop <= k; coop++) {
		// cout << "###" << coop << endl;

		// assume will get coop coop-er at the end
		// dp[i][j] = in [1, i], the actual min cost to get j coop-er and (i - j) no-coop region
		vector<vector<double>> dp(n + 5, vector<double>(k + 5, 1e16));
		for (int i = 0; i <= k; i++) {
			for (int j = 0; j <= min(coop, i); j++) {
				if (i == 0) {
					// miss out the case that no coop-er is needed.
					dp[i][j] = 0;
				}
				else if (i == 1) {
					if (j == 0) dp[i][j] = pl[i].first / (coop + 1.0);
					if (j == 1 && pl[i].second != 1e9) dp[i][j] = pl[i].second;
				}
				else {
					// not choose i as a coop-er
					dp[i][j] = min(dp[i][j], dp[i - 1][j] + pl[i].first / (coop + 1.0));
					// choosing i as a coop-er
					if (j > 0 && pl[i].second != 1e9) {
						dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + pl[i].second / (j - 1 + 1.0));
					}
				}
				// cout << i << " " << j << " " << dp[i][j] << endl;
				if (j == coop) {
					// cout << "@" << i << " " << j << " " << dp[i][j] << " $ " << k - i << " " << suffix[i + 1][k - i] << " " << dp[i][j] + suffix[i + 1][k - i] / (coop + 1.0) << "\n";
					if (i < k) {
						ans = min(ans, dp[i][j] + suffix[i + 1][k - i] / (coop + 1.0));
					}
					else {
						ans = min(ans, dp[i][j]);
					}
				}
			}
		}
	}
	cout << fixed << setprecision(9) << ans << "\n";
}

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 11 / 11
• Subtask 4: 12 / 12
• Subtask 5: 33 / 33
• Subtask 6: 11 / 11
• Subtask 7: 23 / 23