Submission #306447

#	Time	Username	Problem	Language	Result	Execution time	Memory
306447		SorahISA	Counting Mushrooms (IOI20_mushrooms)	C++17	91.87 / 100	10 ms	512 KiB

mushrooms

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

using pii = pair<int, int>;
template<typename T>
using Prior = priority_queue<T>;
template<typename T>
using prior = priority_queue<T, vector<T>, greater<T>>;

#define X first
#define Y second
#define ALL(x) (x).begin(), (x).end()
#define eb emplace_back
#define pb push_back

int count_mushrooms(int n) {
    const int B = (int)floor(sqrt(2 * n + 0.5));
    vector<int> m{0};
    
    // cout << "Block size = " << B << "\n";
    
    if (n <= 227) {
        for (int i = 1; i < n; ++i) {
            m.eb(m.back() ^ use_machine({i-1, i}));
        }
        return n - accumulate(ALL(m), 0);
    }
    
    vector<int> tA{0}, tB;
    m.eb(m.back() ^ use_machine({0, 1}));
    m.back() ? tB.eb(1) : tA.eb(1);
    m.eb(m.back() ^ use_machine({1, 2}));
    m.back() ? tB.eb(2) : tA.eb(2);
    
    for (int i = 3; i < B; i += 2) {
        if (tA.size() >= 2) {
            int ret = use_machine({tA[0], i, tA[1], i + 1});
            ret & 2 ? tB.eb(i) : tA.eb(i);
            ret & 1 ? tB.eb(i + 1) : tA.eb(i + 1);
        }
        else {
            int ret = use_machine({tB[0], i, tB[1], i + 1});
            ret & 2 ? tA.eb(i) : tB.eb(i);
            ret & 1 ? tA.eb(i + 1) : tB.eb(i + 1);
        }
    }
    
    // cout << "tA : "; for (auto x : tA) cout << x << " "; cout << "\n";
    // cout << "tB : "; for (auto x : tB) cout << x << " "; cout << "\n";
    
    int ans = tA.size(), tok = B | 1;
    
    while (tok < n) {
        if (tA.size() >= tB.size()) {
            /// 0 x 0 x 0 x 0 ... 0 x 0 x ///
            int sz = tA.size();
            vector<int> tmp;
            for (int i = 0; i < sz and tok < n; ++i) {
                tmp.eb(tA[i]), tmp.eb(tok++);
            }
            int ret = use_machine(tmp);
            ans += tmp.size() / 2 - (ret + 1) / 2;
            if (~ret & 1) tA.eb(tok - 1);
            else          tB.eb(tok - 1);
        }
        else if (tB.size() > tA.size()) {
            /// 1 x 1 x 1 x 1 ... 1 x 1 x ///
            int sz = tB.size();
            vector<int> tmp;
            for (int i = 0; i < sz and tok < n; ++i) {
                tmp.eb(tB[i]), tmp.eb(tok++);
            }
            int ret = use_machine(tmp);
            ans += (ret + 1) / 2;
            if (ret & 1) tA.eb(tok - 1);
            else         tB.eb(tok - 1);
        }
    }
    
    return ans;
}

• Subtask 1: 91.8699 / 100