Submission #222148

#	Time	Username	Problem	Language	Result	Execution time	Memory
222148		VEGAnn	새로운 문제 (COCI19_akvizna)	C++14	65 / 130	441 ms	640 KiB

Main

#include <bits/stdc++.h>
#define sz(x) ((int)x.size())
#define pii pair<int,int>
#define ft first
#define sd second
#define MP make_pair
#define all(x) x.begin(),x.end()
#define PB push_back
using namespace std;
typedef long long ll;
typedef long double ld;
const int N = 100100;
const ll OO = 1e18;
const ld E = 1e-9;
vector<int> vc;
ld f[2][N];
int n, k, tp;

void calc(int l, int r, int opl, int opr){
    if (l > r) return;

    int j = (l + r) >> 1, opt = -1;

    for (int pr = max(j, opl); pr <= opr; pr++){
        if (f[tp ^ 1][pr] < -E) continue;

        ld ad = f[tp ^ 1][pr] + 1.0 - ld(j) / ld(pr);

        if (f[tp][j] + E < ad) {
            f[tp][j] = ad;
            opt = pr;
        }
    }

    assert(opt > -1);

    calc(l, j - 1, opl, opt);
    calc(j + 1, r, opt, opr);
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);

//    freopen("in.txt","r",stdin);

    cin >> n >> k;

    assert(n <= 3000);

    for (int j = 0; j <= n; j++)
        f[0][j] = -1.0;

    f[0][n] = 0.0;

    for (int i = 1; i <= k; i++) {
        tp = (i & 1);

        for (int j = 0; j <= n; j++)
            f[tp][j] = -1.0;

        calc(0, n - 1, 0, n);
    }

    cout << fixed << setprecision(10) << f[k & 1][0];

    return 0;
}

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