제출 #866539

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
866539		TAhmed33	Ekoeko (COCI21_ekoeko)	C++98	110 / 110	14 ms	7904 KiB

Main

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 2e5 + 25;
struct bit {
	int tree[MAXN] = {};
	void add (int x) {
		if (x < 0 || x > MAXN) return;
		for (; x < MAXN; x += x & (-x)) tree[x]++;
	}
	int get (int x) {
		if (x < 0 || x > MAXN) return 0;
		int sum = 0; for (; x; x -= x & (-x)) sum += tree[x];
		return sum;
	}
} cur;
int n;
string s;
vector <int> occ[26];
int pref[MAXN];
signed main () {
	ios::sync_with_stdio(0); 
	cin.tie(0); memset(cur.tree, 0, sizeof(cur.tree)); 
	cin >> n >> s; 
	s.insert(s.begin(), '0');
	for (int i = 1; i <= 2 * n; i++) occ[s[i] - 'a'].push_back(i);
	vector <pair <int, int>> ll2;
	for (int i = 0; i < 26; i++) {
		if (occ[i].empty()) continue;
		for (int j = (int)occ[i].size() / 2; j < (int)occ[i].size(); j++) {
			ll2.push_back({occ[i][j - (int)occ[i].size() / 2], occ[i][j]});
			pref[occ[i][j]]++;
		}
	}
	sort(ll2.begin(), ll2.end()); ll2.insert(ll2.begin(), {0, 0});
	for (int i = 1; i <= 2 * n; i++) pref[i] += pref[i - 1];
	int sum = 0; int sum2 = 0; for (int i = 1; i <= n; i++) {
		sum += pref[ll2[i].first];
		sum2 += cur.get(ll2[i].second);
		cur.add(ll2[i].second);
	}
	cout << sum + n * (n - 1) / 2 - sum2 << '\n';
}

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