제출 #801810

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
801810		ymm	Seesaw (JOI22_seesaw)	C++17	34 / 100	2036 ms	340 KiB

seesaw

#include <bits/stdc++.h>
#define Loop(x,l,r) for (ll x = (l); x < (r); ++x)
typedef long long ll;
using namespace std;

const int N = 200'010;
double pos[N];
double sum;
int n;

pair<double,double> solve(double l)
{
	double sum = ::sum;
	assert(l <= sum/n);
	int p0 = 0, p1 = n-1;
	double mn = sum/n, mx = sum/n;
	for (int cnt = n; p0 < p1; --cnt) {
		if (l <= (sum-pos[p1])/(cnt-1)) {
			sum -= pos[p1];
			mn = min(mn, sum/(cnt-1));
			--p1;
		} else {
			sum -= pos[p0];
			mx = max(mx, sum/(cnt-1));
			++p0;
		}
	}
	return {mn, mx};
}

int main()
{
	cin.tie(0) -> sync_with_stdio(false);
	cin >> n;
	Loop (i,0,n) {
		ll x;
		cin >> x;
		pos[i] = x;
		sum += pos[i];
	}
	double m = sum/n;
	double ans = m - pos[0];
	double mn = pos[0];
	const double eps = 1e-6;
	while (m-mn > eps) {
		auto [x, y] = solve(mn);
		ans = min(ans, y-x);
		mn = x+eps;
	}
	cout << fixed << setprecision(9);
	cout << ans << '\n';
}

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