제출 #866493

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
866493		TAhmed33	Ekoeko (COCI21_ekoeko)	C++98	0 / 110	1089 ms	2136 KiB

Main

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 1e5 + 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];
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 <= n; i++) occ[s[i] - 'a'].push_back(i);
	for (int i = 0; i < 26; i++) reverse(occ[i].begin(), occ[i].end());
	long long cnt = 0; 
	for (int i = n + 1; i <= 2 * n; i++) {
		int u = occ[s[i] - 'a'].back();
		occ[s[i] - 'a'].pop_back();
		cnt += cur.get(u); cur.add(u);
	}
	cout << n * (n - 1) / 2 - cnt << '\n';
}
/*aabcdffa
adaffacb

1,2,3,4,5,6,7,8
1,5,2,6,7,8,4,3*/

• Subtask 1: 0 / 10
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 20
• Subtask 5: 0 / 40