Submission #1127171

#	Time	Username	Problem	Language	Result	Execution time	Memory
1127171		vladilius	Seesaw (JOI22_seesaw)	C++20	67 / 100	529 ms	48492 KiB

seesaw

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pdi = pair<double, int>;
#define pb push_back
#define ff first
#define ss second

struct ST{
    vector<int> t;
    int n;
    ST(int ns){
        n = ns;
        t.resize(4 * n);
    }
    void upd(int v, int tl, int tr, int& p, int& x){
        if (tl == tr){
            t[v] += x;
            return;
        }
        int tm = (tl + tr) / 2, vv = 2 * v;
        if (p <= tm){
            upd(vv, tl, tm, p, x);
        }
        else {
            upd(vv + 1, tm + 1, tr, p, x);
        }
        t[v] = max(t[vv], t[vv + 1]);
    }
    void upd(int p, int x){
        upd(1, 1, n, p, x);
    }
    int get(){
        return t[1];
    }
};

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    int n; cin>>n;
    vector<int> a(n + 1);
    vector<ll> p(n + 1);
    for (int i = 1; i <= n; i++){
        cin>>a[i];
        p[i] = p[i - 1] + a[i];
    }
    
    if (n > 2e3) return 0;
    
    vector<vector<double>> X(n + 1, vector<double>(n + 1));
    for (int i = 1; i <= n; i++){
        for (int j = i; j <= n; j++){
            X[i][j] = 1.0 * (p[j] - p[i - 1]) / (j - i + 1);
        }
    }
    
    priority_queue<pdi, vector<pdi>, greater<pdi>> pq;
    for (int i = 1; i <= n; i++) pq.push({X[1][n - i + 1], i});
    
    vector<int> t(n + 1, 1);
    vector<pii> all = {{0, 0}};
    int j = 1;
    ST T(n);
    
    double out = 1e9 + 1;
    while (!pq.empty()){
        auto [V, i] = pq.top(); pq.pop();
        int r = t[i] + n - i;

        if (t[i] == 1){
            for (int j = 1; j <= r; j++){
                T.upd(j, 1);
            }
        }
        else {
            T.upd(r, 1);
        }
        
        if (r < n){
            pq.push({X[t[i] + 1][r + 1], i});
        }
        
        all.pb({t[i]++, r});
        
        while (T.get() == n && j < all.size()){
            auto [l, r] = all[j];
            if (r == n) break;
            int ii = n - (r - l);
            
            if (l == (t[ii] - 1)){
                for (int f = t[ii] - 1; f <= t[ii] - 1 + n - ii; f++){
                    T.upd(f, -1);
                }
            }
            else {
                T.upd(l, -1);
            }
            if (T.get() != n){
                if (l == (t[ii] - 1)){
                    for (int f = t[ii] - 1; f <= t[ii] - 1 + n - ii; f++){
                        T.upd(f, 1);
                    }
                }
                else {
                    T.upd(l, 1);
                }
                break;
            }
            j++;
        }
        
        if (T.get() == n){
            auto [l, r] = all[j];
            out = min(out, V - X[l][r]);
        }
    }
    
    cout<<fixed<<setprecision(12)<<out<<"\n";
}

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