Submission #1000325

#	Time	Username	Problem	Language	Result	Execution time	Memory
1000325		MateiKing80	Monochrome Points (JOI20_monochrome)	C++14	4 / 100	1 ms	436 KiB

monochrome

#include <bits/stdc++.h>

using namespace std;

using ll = long long;
#define int ll

string s;
vector<int> w, b;
#define lsb(x) (x & -x)
struct AIB 
{
    vector<int> tree;
    AIB(int n) 
    { 
        tree.assign(n + 5, 0); 
    }
    void upd(int p, int x) 
    {
        while(p < tree.size()) 
            tree[p] += x, p += lsb(p);
    }
    int query(int p) 
    {
        int sum = 0;
        while(p > 0) 
            sum += tree[p], p -= lsb(p);
        return sum;
    }
};

int n;

int nrInv(int k)
{
    int ans = 0;
    AIB ds(2 * n);
    vector<pair<int, int>> v;
    for(int i = 0; i < n; i ++)
        v.push_back({w[i], b[(i + k) % n]});
    for(auto &i : v)
        if(i.first > i.second)
            swap(i.first, i.second);
    sort(v.begin(), v.end());
    for(int i = 0; i < n; i ++)
    {
        //cout << v[i].first << " " << v[i].second << "\n";
        ans += ds.query(v[i].second) - ds.query(v[i].first);
        ds.upd(v[i].second, 1);
    }
    //cout << '\n';
    return ans;
}

signed main()
{
    cin >> n >> s;
    for(int i = 0; i < 2 * n; i ++)
    {
        if(s[i] == 'B')
            b.push_back(i + 1);
        else
            w.push_back(i + 1);
    }
    int pas = (1 << 20), pos = 0;
    while(pas)
    {
        if(pos + pas < n && nrInv(pos + pas - 1) < nrInv(pos + pas))
            pos += pas;
        pas /= 2;
    }
    cout << nrInv(pos);
}

Compilation message (stderr)

monochrome.cpp: In member function 'void AIB::upd(ll, ll)':
monochrome.cpp:20:17: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |         while(p < tree.size())
      |               ~~^~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 0 / 21
• Subtask 3: 0 / 10
• Subtask 4: 0 / 65