Submission #1161846

#	Time	Username	Problem	Language	Result	Execution time	Memory
1161846		Pacybwoah	The Collection Game (BOI21_swaps)	C++20	100 / 100	2 ms	472 KiB

swaps

// batcher's odd-even merge sort
// https://math.mit.edu/~shor/18.310/batcher.pdf
#include "swaps.h"
#include<iostream>
#include<vector>
#include<algorithm>
#include<utility>
#include<string>
using namespace std;
namespace{
    const int maxn = 512;
}
void solve(int n, int v) {
    vector<pair<int, int>> ops;
    vector<int> vec(n);
    for(int i = 0; i < n; i++) vec[i] = i + 1;
    auto add = [&](int a, int b){
        if(a >= n || b >= n) return;
        schedule(vec[a], vec[b]);
        ops.emplace_back(a, b);
        return;
    };
    auto do_ops = [&](){
        auto res = visit();
        int sz = (int)ops.size();
        for(int i = 0; i < sz; i++){
            auto &[a, b] = ops[i];
            if(res[i] == 0) swap(vec[a], vec[b]);
            // whether or not the grader swaps paintings actually doesn't matter!
            // calling comp(a, b) means that we don't know their order yet and whether a or b is bigger doesn't mess up the order
            // in the case of batcher's odd-even merge sort the grouped pairs are already in order
        }
        vector<pair<int, int>>().swap(ops);
        return;
    };
    vector<vector<vector<pair<int, int>>>> srtd(10);
    srtd[1].push_back({make_pair(0, 1)});
    for(int i = 0; i < maxn; i += 2){
        add(i, i + 1);
    }
    do_ops();
    for(int i = 2; i < 10; i++){
        // 0, 2, 4, ..., (1 << i) - 2
        // 1, 3, 5, ..., (1 << i) - 1
        vector<int> odd, even;
        for(int j = 0; j < (1 << i); j += 2) even.push_back(j), odd.push_back(j + 1);
        int sz = (int)srtd[i - 1].size();
        for(int j = 0; j < sz; j++){
            vector<pair<int, int>> now;
            for(auto &[a, b]: srtd[i - 1][j]){
                now.emplace_back(odd[a], odd[b]);
                now.emplace_back(even[a], even[b]);
            }
            srtd[i].push_back(now);
        }
        vector<pair<int, int>> lst_op;
        for(int j = 1; j < (1 << i) - 1; j += 2){
            lst_op.emplace_back(j, j + 1);
        }
        srtd[i].push_back(lst_op);
        for(auto &now: srtd[i]){
            for(auto [a, b]: now){
                while(a < maxn && b < maxn){
                    add(a, b);
                    a += (1 << i);
                    b += (1 << i);
                }
            }
            do_ops();
        }
    }
    answer(vec);
}
// g++ -std=c++20 -Wall -Wextra -Wshadow -fsanitize=undefined -fsanitize=address -o run swaps.cpp grader.cpp

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3-1: 3 / 3
• Subtask 3-2: 2 / 2
• Subtask 4-1: 9 / 9
• Subtask 4-2: 6 / 6
• Subtask 5-1: 9 / 9
• Subtask 5-2: 6 / 6
• Subtask 6-1: 21 / 21
• Subtask 6-2: 14 / 14
• Subtask 7-1: 9 / 9
• Subtask 7-2: 6 / 6