Submission #854498

#	Time	Username	Problem	Language	Result	Execution time	Memory
854498		vjudge1	Seesaw (JOI22_seesaw)	C++17	67 / 100	343 ms	15948 KiB

seesaw

#include <bits/stdc++.h>
using namespace std;

class fraction_t {
       public:
        int64_t x, y;

        // x / y, normalized to y > 0 if x != 0 and y = 1 if x = 0

        void fix() {
                assert(y && "Your Denominator Equal 0");
                int64_t d = __gcd(abs(x), y);
                x /= d;
                y /= d;
        }

        fraction_t(const int64_t& x = 0, const int64_t& y = 1) : x(x), y(y) { fix(); }

        friend bool operator<(const fraction_t& e, const fraction_t& f) { return e.x * f.y < e.y * f.x; }
        friend bool operator<=(const fraction_t& e, const fraction_t& f) { return e.x * f.y <= e.y * f.x; }
        friend bool operator==(const fraction_t& e, const fraction_t& f) { return e.x * f.y == e.y * f.x; }
        friend bool operator!=(const fraction_t& e, const fraction_t& f) { return e.x * f.y != e.y * f.x; }
        friend bool operator>(const fraction_t& e, const fraction_t& f) { return e.x * f.y > e.y * f.x; }
        friend bool operator>=(const fraction_t& e, const fraction_t& f) { return e.x * f.y >= e.y * f.x; }
        friend ostream& operator<<(ostream& out, const fraction_t& f) {
                out << setprecision(11) << fixed << ((double)f.x) / f.y;
                return out;
        }
};

int32_t main() {
        ios_base::sync_with_stdio(0);
        cin.tie(0);
        int n;
        cin >> n;
        vector<int> a(n);
        for (int i = 0; i < n; i++) cin >> a[i];
        vector<int64_t> pref(n + 1, 0);
        for (int i = 0; i < n; i++) pref[i + 1] = pref[i] + a[i];
        fraction_t c(pref[n] - pref[0], n);
        set<pair<fraction_t, int>> s;
        vector<int> nxt(n, -1);
        for (int i = n - 1; i > 0; i--) {
                int l = 0, r = n - i, fl;
                while (l <= r) {
                        int mid = l + r >> 1;
                        if (fraction_t(pref[mid + i] - pref[mid], i) <= c) {
                                fl = mid;
                                l = mid + 1;
                        } else {
                                r = mid - 1;
                        }
                }

                fraction_t f(pref[fl + i] - pref[fl], i);
                if (f != c) {
                        if (fl + 1 + i <= n) nxt[i] = fl + 1;
                }

                s.emplace(f, i);
        }
        s.emplace(c, 0);

        long double res = 1e18;

        while (true) {
                auto [f, i] = *s.begin();
                auto a = s.rbegin()->first;
                auto b = s.begin()->first;
                long double aa = (long double)a.x / a.y;
                long double bb = (long double)b.x / b.y;
                res = min(res, aa - bb);
                s.erase(s.begin());
                if (nxt[i] == -1) break;
                s.emplace(fraction_t(pref[nxt[i] + i] - pref[nxt[i]], i), i);
                nxt[i] = -1;
        }

        cout << fixed << setprecision(11) << res;
}

Compilation message (stderr)

seesaw.cpp: In function 'int32_t main()':
seesaw.cpp:46:37: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   46 |                         int mid = l + r >> 1;
      |                                   ~~^~~
seesaw.cpp:55:52: warning: 'fl' may be used uninitialized in this function [-Wmaybe-uninitialized]
   55 |                 fraction_t f(pref[fl + i] - pref[fl], i);
      |                                                    ^

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