Submission #855912

#	Time	Username	Problem	Language	Result	Execution time	Memory
855912		wakandaaa	새로운 문제 (COCI19_akvizna)	C++17	130 / 130	188 ms	4168 KiB

Main

#include <bits/stdc++.h>
#define int long long
#define double long double

using namespace std;

#define mp make_pair
#define fi first
#define se second
#define all(x) x.begin(), x.end()

#define getbit(x, i) (((x) >> (i)) & 1)
#define bit(x) (1 << (x))
#define popcount __builtin_popcountll

mt19937_64 rd(chrono::steady_clock::now().time_since_epoch().count());
long long rand(long long l, long long r) {
    return l + rd() % (r - l + 1);
}

const int N = 1e6 + 5;
const int mod = 1e9 + 7; // 998244353;
const int lg = 25; // lg + 1
const int inf = 1e9; // INT_MAX;
const long long llinf = 1e18; // LLONG_MAX;

template<class X, class Y>
bool minimize(X &a, Y b) {
    return a > b ? (a = b, true) : false;
}

template<class X, class Y>
bool maximize(X &a, Y b) {
    return a < b ? (a = b, true) : false;
}

template<class X, class Y>
bool add(X &a, Y b) {
    a += b;
    while (a >= mod) a -= mod;
    while (a < 0) a += mod;
    return true;
}

const double eps = 1e-10;

int n, k;
int cnt[N];
double f[N];

double F(int j, int k) {
    return (f[j] - f[k]) / (j - k);
}

bool ok(double mid) {
    deque<int> q;
    q.push_back(0);
    for (int i = 1; i <= n; ++i) {
        while (q.size() >= 2 && F(q[0], q[1]) > 1.0 / i) q.pop_front();
        int j = q.front();
        f[i] = f[j] + (double) (i - j) / i - mid;
        cnt[i] = cnt[j] + 1;
        while (q.size() >= 2 && F(q[q.size() - 2], q[q.size() - 1]) < F(q[q.size() - 1], i)) q.pop_back();
        q.push_back(i);
    }
    return cnt[n] >= k;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    cin >> n >> k;
    double l = 0, r = 1e9, mid;
    while (r - l >= eps) {
        mid = (l + r) / 2;
        if (ok(mid)) l = mid; else r = mid;
    }

    cout.precision(12);
    cout << fixed;
    cout << f[n] + (double) mid * k;

    return 0;
}

/*

*/

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