Submission #540814

#	Time	Username	Problem	Language	Result	Execution time	Memory
540814		AlperenT	Ekoeko (COCI21_ekoeko)	C++17	110 / 110	14 ms	3652 KiB

Main

#include <bits/stdc++.h>

using namespace std;

const int N = (1e5 + 5) * 2;

int n, cnt[26];
long long ans;

string str;

vector<char> strv;

vector<int> indx[26], v;

struct Fenwick{
    int tree[N];

    int getsum(int r){
        int sum = 0;
        for(int i = r; i > 0; i -= i & -i) sum += tree[i];
        return sum;
    }

    int query(int l, int r){
        if(l > r) return 0;
        return getsum(r) - getsum(l - 1);
    }

    void update(int pos, int val){
        for(int i = pos; i < N; i += i & -i) tree[i] += val;
    }
};

Fenwick fw;

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

    cin >> n;
    cin >> str;

    n *= 2;

    for(auto c : str) cnt[c - 'a']++;

    for(int i = 0; i < n; i++){
        if(cnt[str[i] - 'a'] > 0){
            strv.push_back(str[i]);
            cnt[str[i] - 'a'] -= 2;
        }
    }

    for(int i = 0, m = strv.size(); i < m; i++) strv.push_back(strv[i]);

    for(int i = 0; i < n; i++) indx[strv[i] - 'a'].push_back(i + 1);

    for(int i = 0; i < 26; i++) reverse(indx[i].begin(), indx[i].end());

    for(int i = 0; i < n; i++){
        v.push_back(indx[str[i] - 'a'].back());
        indx[str[i] - 'a'].pop_back();
    }

    for(auto i : v){
        ans += fw.query(i + 1, n);
        fw.update(i, 1);
    }

    cout << ans;
}

• Subtask 1: 10 / 10
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 20 / 20
• Subtask 5: 40 / 40