Submission #306460

#	Time	Username	Problem	Language	Result	Execution time	Memory
306460		SorahISA	Counting Mushrooms (IOI20_mushrooms)	C++17	74.10 / 100	10 ms	384 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) {
    srand(time(NULL));
    const int B = (int)floor(sqrt(4 * 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);
    }
    
    int ret;
    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);
    
    if (tA.size() >= 2) {
        ret = use_machine({tA[0], 3, tA[1], 4});
        ret & 2 ? tB.eb(3) : tA.eb(3);
        ret & 1 ? tB.eb(4) : tA.eb(4);
    }
    else {
        ret = use_machine({tB[0], 3, tB[1], 4});
        ret & 2 ? tA.eb(3) : tB.eb(3);
        ret & 1 ? tA.eb(4) : tB.eb(4);
    }
    
    for (int i = 5; i < B; i += 3) {
        int fl = tA.size() >= 3 ? 1 : 0;
        if (tA.size() >= 3 and tB.size() >= 3) fl = rand() & 1;
        if (fl) {
            ret = use_machine({tA[0], i, tA[1], i+1, tA[2], i+2});
            ret & 1 ? tB.eb(i+2) : tA.eb(i+2);
            if (ret & 2) {
                ret = use_machine({tA[0], i, tA[1], i+1});
                ret & 1 ? tB.eb(i+1) : tA.eb(i+1);
                ret & 2 ? tB.eb(i) : tA.eb(i);
            }
            else {
                if (ret & 4) tB.eb(i), tB.eb(i+1);
                else         tA.eb(i), tA.eb(i+1);
            }
        }
        else {
            ret = use_machine({tB[0], i, tB[1], i+1, tB[2], i+2});
            ret & 1 ? tA.eb(i+2) : tB.eb(i+2);
            if (ret & 2) {
                ret = use_machine({tB[0], i, tB[1], i+1});
                ret & 1 ? tA.eb(i+1) : tB.eb(i+1);
                ret & 2 ? tA.eb(i) : tB.eb(i);
            }
            else {
                if (ret & 4) tA.eb(i), tA.eb(i+1);
                else         tB.eb(i), tB.eb(i+1);
            }
        }
    }
    
    sort(ALL(tA)), sort(ALL(tB));
    
    // 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 = max(tA.size() ? tA.back() : 0LL,
                                   tB.size() ? tB.back() : 0LL) + 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++);
            }
            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++);
            }
            ret = use_machine(tmp);
            ans += (ret + 1) / 2;
            if (ret & 1) tA.eb(tok - 1);
            else         tB.eb(tok - 1);
        }
    }
    
    return ans;
}

• Subtask 1: 74.0984 / 100