Submission #1115022

#	Time	Username	Problem	Language	Result	Execution time	Memory
1115022		mightyrock	Counting Mushrooms (IOI20_mushrooms)	C++17	99.56 / 100	9 ms	848 KiB

mushrooms

#include "mushrooms.h"
#include <bits/stdc++.h>

#define vi vector<int>
#define pb push_back

using namespace std;

const int maxn = 20000;
vi shroom[2] = {{0},{}};
int uses = 0;
int type[maxn] = {0};

void found(int ind, int val) {
    type[ind] = val;
    shroom[val].pb(ind);
}

void start(int sec) {
    //test A_
    vi test = {0,sec};
    int res = use_machine(test);
    ++uses;
    found(sec,res);
}

void start2(vi probe) {
    //test A_A_
    vi test;
    int cur = (shroom[0].size() >= shroom[1].size()) ? 0 : 1;
    int opp = !cur;
    for (int i=0; i<2; ++i) {
        test.pb(shroom[cur][i]);
        test.pb(probe[i]);
    }
    int res = use_machine(test);
    ++uses;
    int l = probe[0], r = probe[1];
    if (res%2 == 0) {
        found(r,cur);
    } else {
        found(r,opp);
        --res;
    }
    if (res == 0) {
        found(l,cur);
    } else {
        found(l,opp);
    }
}

int quad(vi probe) {
    //test A_A_A_A_
    vi test;
    int cur = (shroom[0].size() >= shroom[1].size()) ? 0 : 1;
    int opp = !cur;
    int k = probe.size();
    for (int i=0; i<k; ++i) {
        test.pb(shroom[cur][i]);
        test.pb(probe[i]);
    }
    int res = use_machine(test);
    ++uses;
    int last = probe[k-1];
    if (res%2 == 0) {
        found(last,cur);
    } else {
        found(last,opp);
        --res;
    }
    if (res == 0) {
        for (int i=0; i<k-1; ++i) {
            found(probe[i],cur);
        }
    } else if (res == 6) {
        for (int i=0; i<k-1; ++i) {
            found(probe[i],opp);
        }
    }
    return res;
}

void test1(vi probe) {
    //test A_A_A_A_ while we have less than 2 B's
    int cur = (shroom[0].size() >= shroom[1].size()) ? 0 : 1;
    int opp = !cur;
    int res = quad(probe);
    int l = probe[0], m = probe[1], r = probe[2];
    if (res == 2) {
        vi subtest = {l,m};
        start2(subtest);
        if (type[l] == cur && type[m] == cur) {
            found(r, opp);
        } else {
            found(r,cur);
        }
    } else if (res == 4) {
        vi subtest = {l,m};
        start2(subtest);
        if (type[l] == opp && type[m] == opp) {
            found(r,cur);
        } else {
            found(r,opp);
        }
    }
}

void subtest2(vi probe, int cur) {
    //test A_A__B if we know probe is a permutation of (ABB)
    //test B_B__A if (AAB)
    //future george here: YOU FORGOT THE FREE SHROOM
    vi test;
    int opp = !cur;
    int l = probe[0], m = probe[1], r = probe[2], rr = probe[3];
    test = {shroom[cur][0], l, shroom[cur][1], m, r, shroom[opp][0], rr};
    int res = use_machine(test);
    ++uses;
    if (res%2 == 0) {
        found(rr,cur);
        --res;
    } else {
        found(rr,opp);
    }
    if (res == 1) {
        found(l,cur);
        found(m,opp);
        found(r,opp);
    } else if (res == 3) {
        found(l,opp);
        found(m,cur);
        found(r,opp);
    } else if (res == 5) {
        found(l,opp);
        found(m,opp);
        found(r,cur);
    }
    return;
}

bool test2(vi probe) {
    //test A_A_A_A_ when we already have 2 B's
    //future george here: YOU FORGOT THE FREE SHROOM
    vi test = probe;
    test.pop_back();
    int cur = (shroom[0].size() >= shroom[1].size()) ? 0 : 1;
    int opp = !cur;
    int res = quad(test);
    //forgot case res 0, res 6 - free shroom is lost
    //fixed with bool - true if we are instantly done
    test.pop_back();
    test.pb(probe.back());
    if (res == 2) {
        subtest2(test, opp);
        return false;
    } else if (res == 4) {
        subtest2(test, cur);
        return false;
    }
    return true;
}

int test3(vi probe) {
    //test A_A_A_......A_A_
    vi test;
    int cur = (shroom[0].size() >= shroom[1].size()) ? 0 : 1;
    int opp = !cur;
    int k = probe.size();
    for (int i=0; i<k; ++i) {
        test.pb(shroom[cur][i]);
        test.pb(probe[i]);
    }
    int res = use_machine(test);
    ++uses;
    int last = probe[k-1];
    if (res%2 == 0) {
        found(last,cur);
    } else {
        found(last,opp);
        --res;
    }
    int numcur = res/2;
    if (cur == 0) {
        return k-1-numcur;
    }
    return numcur;
}

int count_mushrooms(int n) {
    int count_a = 0;
    int magic = 90;
    for (int i=0; i<n; ++i) {
        type[i] = -1;
    }
    if (n <= 221) {
        for (int i = 1; i<n; ++i) {
            start(i);
        }
        return shroom[0].size();
    }
    int ind = 1;
    while (shroom[0].size() < 2 && shroom[1].size()<2) {
        start(ind);
        ++ind;
    }
    while (shroom[0].size() < 4 && shroom[1].size()<4) {
        vi probe = {ind, ind+1};
        start2(probe);
        ind +=2;
    }
    int cur = (shroom[0].size() >= shroom[1].size()) ? 0 : 1;
    int opp = !cur;
    while (shroom[opp].size() < 2 && shroom[cur].size() < magic) {
        vi probe;
        for (int i=0; i<4; ++i) {
            probe.pb(ind);
            ++ind;
        }
        test1(probe);
    }
    cur = (shroom[0].size() >= shroom[1].size()) ? 0 : 1;
    opp = !cur;
    while (shroom[cur].size() < magic) {
        vi probe;
        for (int i=0; i<5; ++i) {
            probe.pb(ind);
            ++ind;
        }
        bool quick = test2(probe);
        if (quick) {
            --ind; //if the first 3 are the same, we don't need an extra check just for the last free shroom, just do it in the next batch
        }
        cur = (shroom[0].size() >= shroom[1].size()) ? 0 : 1;
        opp = !cur;
        // cout << "excluding ind " << ind << " we found " << shroom[0].size() << "\n";
    }
    int s = shroom[0].size();
    while (ind != n) {
        cur = (shroom[0].size() >= shroom[1].size()) ? 0 : 1;
        opp = !cur;
        int s = shroom[cur].size();
        int cap = min(s, n-ind);
        vi probe;
        for (int i=0; i<cap; ++i) {
            probe.pb(ind);
            ++ind;
        }
        count_a += test3(probe);
    }
    return count_a + shroom[0].size();
}

Compilation message (stderr)

mushrooms.cpp: In function 'int count_mushrooms(int)':
mushrooms.cpp:212:57: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  212 |     while (shroom[opp].size() < 2 && shroom[cur].size() < magic) {
      |                                      ~~~~~~~~~~~~~~~~~~~^~~~~~~
mushrooms.cpp:222:31: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  222 |     while (shroom[cur].size() < magic) {
      |            ~~~~~~~~~~~~~~~~~~~^~~~~~~
mushrooms.cpp:236:9: warning: unused variable 's' [-Wunused-variable]
  236 |     int s = shroom[0].size();
      |         ^

• Subtask 1: 99.5595 / 100