Submission #854678

#	Time	Username	Problem	Language	Result	Execution time	Memory
854678		boris_mihov	Seesaw (JOI22_seesaw)	C++17	0 / 100	0 ms	348 KiB

seesaw

#include <algorithm>
#include <iostream>
#include <iomanip>
#include <numeric>
#include <cassert>
#include <vector>

typedef long long llong;
const int MAXN = 200000 + 10;
const int INF  = 1e9;

int n;
int a[MAXN];

int check2(long double l, long double r)
{
    llong sum = 0;
    for (int i = 1 ; i <= n ; ++i)
    {
        sum += a[i];
    }

    int lPtr = 1, rPtr = n;
    while (lPtr <= rPtr)
    {
        if (sum / (double)(rPtr - lPtr + 1) < l || sum / (double)(rPtr - lPtr + 1) > r)
        {
            return false;
        }

        if (lPtr == rPtr)
        {
            break;
        }
        
        if ((sum - a[rPtr]) / (double)(rPtr - lPtr) >= l)
        {
            sum -= a[rPtr];
            rPtr--;
        } else
        {
            sum -= a[lPtr];
            lPtr++;
        }
    }

    return true;
}

bool check(long double w)
{
    for (int i = 1 ; i <= n ; ++i)
    {
        llong sum = 0;
        for (int j = i ; j <= n ; ++j)
        {
            sum += a[j];
            if (check2(sum / (long double)(j - i + 1), sum / (long double)(j - i + 1) + w))
            {
                return true;
            }
        }
    }

    return false;
}

void solve()
{
    long double l = 0.0, r = INF, mid;
    for (int i = 0 ; i < 64 ; ++i)
    {
        mid = (l + r) / 2.0;
        if (!check(mid)) l = mid;
        else r = mid;
    }

    std::cout << std::fixed << std::setprecision(10) << r << '\n';
}

void input()
{
    std::cin >> n;
    for (int i = 1 ; i <= n ; ++i)
    {
        std::cin >> a[i];
    }
}

void fastIOI()
{
    std::ios_base :: sync_with_stdio(0);
    std::cout.tie(nullptr);
    std::cin.tie(nullptr);
}

int main()
{
    fastIOI();
    input();
    solve();

    return 0;
}

• Subtask 1: 0 / 1
• Subtask 2: 0 / 33
• Subtask 3: 0 / 33
• Subtask 4: 0 / 33