Submission #365766

#	Time	Username	Problem	Language	Result	Execution time	Memory
365766		jasen_penchev	Cheerleaders (info1cup20_cheerleaders)	C++14	100 / 100	1220 ms	7388 KiB

cheerleaders

#include <algorithm>
#include <iostream>
#include <utility>
#include <string>
#include <vector>
#define endl '\n'
using namespace std;

const int MAXN = 17;

int N;
int a[(1ll << MAXN) + 5];
int b[(1ll << MAXN) + 5];
long long cnt1[MAXN + 5], cnt2[MAXN + 5];

void rec(int l, int r, int depth, vector< pair<int, int> > v)
{
    if (r - l == 1) return;

    int mid = (l + r) / 2;
    vector< pair<int, int> > v1, v2;
    for (int i = 0; i < v.size(); ++ i)
    {
        if (v[i].second < mid) v1.push_back(v[i]);
        else v2.push_back(v[i]);
    }
    int pos = 0;
    for (int i = 0; i < v2.size(); ++ i)
    {
        while (pos < v1.size() and v1[pos].first < v2[i].first) pos++;
        cnt1[depth] += pos;
        cnt2[depth] += (mid - l) - pos;
    }
    rec(l, mid, depth + 1, v1);
    rec(mid, r, depth + 1, v2);
}

void split()
{
    for (int i = 0; i < (1ll << N); ++ i)
    {
        if (i % 2 == 0) b[i / 2] = a[i];
        else b[i / 2 + (1ll << (N - 1))] = a[i];
    }
    for (int i = 0; i < (1ll << N); ++ i)
    {
        a[i] = b[i];
    }
}

int main()
{
    ios :: sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    cin >> N;

    for (int i = 0; i < (1ll << N); ++ i)
    {
        cin >> a[i];
    }

    long long answer_inv = (long long)(1e18);
    if (N == 0) answer_inv = 0;
    string answer_moves = "";

    for (int i = 0; i < N; ++ i)
    {
        vector< pair<int, int> > v;
        for (int j = 0; j < (1ll << N); ++ j)
        {
            v.push_back(make_pair(a[j], j));
        }
        sort(v.begin(), v.end());

        for (int j = 0; j < N; ++ j)
        {
            cnt1[j] = 0;
            cnt2[j] = 0;
        }
        rec(0, (1ll << N), 0, v);

        long long sum = 0;
        for (int j = 0; j < N; ++ j)
        {
            sum += min(cnt1[j], cnt2[j]);
        }

        if (answer_inv > sum)
        {
            answer_inv = sum;
            answer_moves = "";
            for (int j = 0; j < i; ++ j) answer_moves += '2';
            for (int j = 0; j < N; ++ j)
            {
                answer_moves += '2';
                if (cnt1[N - 1 - j] < cnt2[N - 1 - j]) answer_moves += '1';
            }
        }
        split();
    }

    cout << answer_inv << endl;
    cout << answer_moves << endl;

    return 0;
}

Compilation message (stderr)

cheerleaders.cpp: In function 'void rec(int, int, int, std::vector<std::pair<int, int> >)':
cheerleaders.cpp:22:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   22 |     for (int i = 0; i < v.size(); ++ i)
      |                     ~~^~~~~~~~~~
cheerleaders.cpp:28:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   28 |     for (int i = 0; i < v2.size(); ++ i)
      |                     ~~^~~~~~~~~~~
cheerleaders.cpp:30:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   30 |         while (pos < v1.size() and v1[pos].first < v2[i].first) pos++;
      |                ~~~~^~~~~~~~~~~

• Subtask 1: 16 / 16
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 21 / 21
• Subtask 5: 28 / 28