Submission #303599

#	Time	Username	Problem	Language	Result	Execution time	Memory
303599		jtnydv25	Counting Mushrooms (IOI20_mushrooms)	C++17	81.59 / 100	943 ms	656 KiB

mushrooms

#include "mushrooms.h"
#include <bits/stdc++.h>
using namespace std;
const int M = 8;
 
int val[200005];
struct node{
	vector<int> states;
	node* res[M];
	vector<int> ask;
	int maxQueries;
	node(){
		for(int i = 0; i < M; i++) res[i] = NULL;
		maxQueries = 0;
	}
	void compute(){
		int n = states.size();
		if(n == 1) return;
		maxQueries = 1;
		int mn = 1 << 20;
		for(int mask = 1; mask < (1 << M); mask++){
			vector<int> perm;
            for(int j = 0; j < M; j++) if(mask >> j & 1) perm.push_back(j);
            if(((int)perm.size()) == 1) continue;
            do{
                vector<int> num(M);
                for(int s : states){
                    int r = 0;
                    for(int j = 0; j + 1 < (int)perm.size(); j++) r += (s >> perm[j] & 1) != (s >> perm[j + 1] & 1);
                    num[r]++;
                }
                int V = *max_element(num.begin(), num.end());
                if(V < mn){
                    mn = V;
                    ask = perm;
                }
            }while(next_permutation(perm.begin(), perm.end()));
		}
        vector<int> perm = ask;
 
		vector<vector<int>> childStates(M);
		
        for(int s : states){
            int r = 0;
            for(int j = 0; j + 1 < (int)perm.size(); j++) r += (s >> perm[j] & 1) != (s >> perm[j + 1] & 1);
            childStates[r].push_back(s);
        }
		for(int i = 0; i < M; i++){
			if(!childStates[i].empty()){
				res[i] = new node();
				res[i]->states = childStates[i];
				res[i]->compute();
				maxQueries = max(maxQueries, res[i]->maxQueries + 1);
			}
		}
	}
    void get(vector<int> positions){
        if((int)states.size() == 1){
            for(int i = 0; i < M; i++) val[positions[i]] = states[0] >> i & 1;
            return;
        }
 
        vector<int> x;
        for(int i : ask) x.push_back(positions[i]);
        res[use_machine(x)]->get(positions);
    }
};
 
int get(int pos){
    return val[pos] = use_machine({0, pos});
}
 
struct decision_tree{
	node * root;
	decision_tree(){
		root = new node();
		for(int i = 0; i < (1 << M); i+=2) root->states.push_back(i);
		root->compute();
	}
    void get(vector<int> positions){
        root->get(positions);
    }
};
 
const int K = 400;
 
int count_mushrooms(int N) {
	decision_tree DT;
    int n = min(N, K);
    // int n = N;
    // for(int j = 1; j < N; j++) get(j);
    for(int i = 1; i < n; i += M - 1){
        int st = i, en = i + M - 2;
        if(en < n){
            vector<int> positions = {0};
            for(int j = st; j <= en; j++) positions.push_back(j);
            DT.get(positions);
        } else{
            for(int j = st; j < n; j++) get(j);
        }
    }
 
    int curr = n - accumulate(val, val + n, 0);
    if(n == N) return curr;
	vector<vector<int>> where(2);
    for(int i = 0; i < n; i++) where[val[i]].push_back(i);
    int id = (int)where[1].size() > (int) where[0].size();
    int R = where[id].size() - 1;
    for(int i = n; i < N; i += R){
        int st = i, en = min(N - 1, i + R - 1);
        vector<int> positions = {where[id][0]};
        for(int j = 0; j <= en - st; j++){
            positions.push_back(st + j);
            positions.push_back(where[id][j + 1]);
        }
        int V = use_machine(positions);
        assert(V % 2 == 0);
        V /= 2;
        if(id == 1) curr += V;
        else curr += en - st + 1 - V;
    }
    return curr;
}

• Subtask 1: 81.5884 / 100