Submission #877986

#	Time	Username	Problem	Language	Result	Execution time	Memory
877986		loncacbuoidai	Sure Bet (CEOI17_sure)	C++14	100 / 100	680 ms	3924 KiB

sure

#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 5;

int n, k;
double a[N], b[N];

bool check(double f) {
	// cerr << fixed << setprecision(10) << f << '\n';

	int x = ([&] () -> int {
		int l = 1, r = n, ans = n * 3;
		while (l <= r) {
			int mid = (l + r) / 2;
			if ((double)a[mid] - k >= f) {
				ans = mid;
				r = mid - 1;
			} else l = mid + 1;
		}
		return ans;
	}());
	int y = ([&] () -> int {
		int l = 1, r = n, ans = n * 3;
		while (l <= r) {
			int mid = (l + r) / 2;
			if ((double)b[mid] - k >= f) {
				ans = mid;
				r = mid - 1;
			} else l = mid + 1;
		}
		return ans;
	}());
	// cerr << x << ' ' << y << " ok " << (x + y <= k) << '\n';
	return x + y <= k;
}

int32_t main() {
	cin.tie(0)->sync_with_stdio(0);
	if (fopen("OXBET.inp", "r"))
		freopen("OXBET.inp", "r", stdin),
		freopen("OXBET.out", "w", stdout);
	
	cin >> n;
	for (int i = 1; i <= n; i++)
		cin >> a[i] >> b[i];
	
	sort(a + 1, a + n + 1, greater<double>());
	sort(b + 1, b + n + 1, greater<double>());
	for (int i = 1; i <= n; i++)
		a[i] += a[i - 1], b[i] += b[i - 1];
	
	// for (int i = 1; i <= n; i++)
		// cerr << a[i] << ' ' << b[i] << '\n';
	
	// k = 3;
	// check(0.5) << '\n';
	// return 0;
	
	double res = 0;
	for (k = 1; k <= n * 2; k++) {
		// cerr << "k  = " << k << '\n';
		double l = 0, r = 2e8, ans = 0;
		for (int t = 1; t <= 50; t++) {
			double mid = (l + r) / 2;
			if (check(mid)) {
				ans = mid;
				l = mid;
			} else r = mid;
		}
		
		res = max(res, ans);
	}
	
	cout << fixed << setprecision(4) << res;
	
	return 0;
}

Compilation message (stderr)

sure.cpp: In function 'int32_t main()':
sure.cpp:41:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   41 |   freopen("OXBET.inp", "r", stdin),
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
sure.cpp:42:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   42 |   freopen("OXBET.out", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 40 / 40
• Subtask 3: 40 / 40