Submission #615340

#	Time	Username	Problem	Language	Result	Execution time	Memory
615340		wiwiho	Seesaw (JOI22_seesaw)	C++14	100 / 100	321 ms	22764 KiB

seesaw

#include <bits/stdc++.h>
#include <bits/extc++.h>

#define StarBurstStream ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define iter(a) a.begin(), a.end()
#define riter(a) a.rbegin(), a.rend()
#define lsort(a) sort(iter(a))
#define gsort(a) sort(riter(a))
#define pb(a) push_back(a)
#define eb(a) emplace_back(a)
#define pf(a) push_front(a)
#define ef(a) emplace_front(a)
#define pob pop_back()
#define pof pop_front()
#define mp(a, b) make_pair(a, b)
#define F first
#define S second
#define mt make_tuple
#define gt(t, i) get<i>(t)
#define tomax(a, b) ((a) = max((a), (b)))
#define tomin(a, b) ((a) = min((a), (b)))
#define topos(a) ((a) = (((a) % MOD + MOD) % MOD))
#define uni(a) a.resize(unique(iter(a)) - a.begin())
#define printv(a, b) {bool pvaspace=false; \
for(auto pva : a){ \
    if(pvaspace) b << " "; pvaspace=true;\
    b << pva;\
}\
b << "\n";}

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<ld, ld>;
using tiii = tuple<int, int, int>;

const ll MOD = 1000000007;
const ll MAX = 2147483647;

template<typename A, typename B>
ostream& operator<<(ostream& o, pair<A, B> p){
    return o << '(' << p.F << ',' << p.S << ')';
}

ll ifloor(ll a, ll b){
    if(b < 0) a *= -1, b *= -1;
    if(a < 0) return (a - b + 1) / b;
    else return a / b;
}

ll iceil(ll a, ll b){
    if(b < 0) a *= -1, b *= -1;
    if(a > 0) return (a + b - 1) / b;
    else return a / b;
}

struct Comp{
    bool operator()(pll xc, pll yc){
        return (__int128)xc.F * yc.S < (__int128)yc.F * xc.S;
    }
};

void waassert(bool t){
    if(t) return;
    cout << "WA\n";
    exit(0);
}

int main(){
    StarBurstStream

    int n;
    cin >> n;

    vector<ll> a(n + 1), s(n + 1);
    for(int i = 1; i <= n; i++) cin >> a[i], s[i] = s[i - 1] + a[i];

    auto getcen = [&](int l, int r){
        return mp(s[r] - s[l - 1], r - l + 1);
    };
    auto comp = [&](pll xc, pll yc){
        return (__int128)xc.F * yc.S < (__int128)yc.F * xc.S;
    };
    auto getdis = [&](pll x, pll y){
        ld tx = (ld)x.F / x.S;
        ld ty = (ld)y.F / y.S;
        return abs(tx - ty);
    };
    
    pll mid = getcen(1, n);
    vector<pii> good;
    vector<pii> lg(n + 1), rg(n + 1);
    lg[n] = rg[n] = mp(1, n);

    for(int i = 0; i < n - 1; i++){
        {
            int l = 1, r = n - i;
            while(l < r){
                int m = (l + r) / 2;
                if(comp(getcen(m, m + i), mid)) l = m + 1;
                else r = m;
            }
            rg[i + 1] = mp(l, l + i);
        }
        {
            int l = 1, r = n - i;
            while(l < r){
                int m = (l + r + 1) / 2;
                if(comp(mid, getcen(m, m + i))) r = m - 1;
                else l = m;
            }
            good.eb(mp(l, l + i));
            lg[i + 1] = mp(l, l + i);
        }
    }
    /*printv(lg, cerr);
    printv(rg, cerr);*/

    sort(iter(good), [&](pii x, pii y){ return comp(getcen(x.F, x.S), getcen(y.F, y.S)); });
    reverse(iter(good));

    multiset<pll, Comp> st;
    for(int i = 1; i <= n; i++){
        st.insert(getcen(rg[i].F, rg[i].S));
    }

    ld ans = getdis(*st.begin(), *st.rbegin());
    /*cerr << "test ";
    printv(st, cerr);*/
    for(pll i : good){
        int len = i.S - i.F + 1;
        auto it = st.find(getcen(rg[len].F, rg[len].S));
        st.erase(it);
        st.insert(getcen(i.F, i.S));
        /*cerr << "test " << i << " : ";
        printv(st, cerr);*/
        ans = min(ans, getdis(*st.begin(), *st.rbegin()));
    }

    cout << fixed << setprecision(20) << ans << "\n";

    return 0;
}

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