Submission #707577

#	Time	Username	Problem	Language	Result	Execution time	Memory
707577		Trisanu_Das	Ekoeko (COCI21_ekoeko)	C++17	110 / 110	13 ms	2728 KiB

Main

#include <bits/stdc++.h>
using namespace std;
 
#define ll long long
#define ar array
 
const int mxN=1e5;
int n, cnt[26], p[mxN], ft[mxN+1];
string s, a, b;
ll ans;
vector<int> oc1[26], oc2[26];
 
void upd(int i) {
	for (++i; i <= n; i += i & -i) ++ft[i];
}
 
int qry(int i) {
	int ans = 0;
	for (++i; i > 0; i -= i & -i) ans += ft[i];
	return ans;
}

int main() {
	cin >> n >> s;
	for (char c : s) ++cnt[c-'a'];
	for (int i=0; i<26; ++i) cnt[i] /= 2;
	for (int i = 0, x = 0; i < 2*n; ++i) {
		if (cnt[s[i]-'a']) a += s[i], ans += x, --cnt[s[i]-'a'];
		else b += s[i], ++x;
	}
	for (int i = 0; i < n; ++i) {
		oc1[a[i] - 'a'].push_back(i);
		oc2[b[i] - 'a'].push_back(i);
	}
	for (int i = 0; i < 26; ++i)
		for (int j=0; j<oc1[i].size(); ++j)
			p[oc2[i][j]] = oc1[i][j];
	for (int i=0; i<n; ++i) {
		ans += i - qry(p[i]);
		upd(p[i]);
	}
	cout << ans << '\n';
	return 0;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:36:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   36 |   for (int j=0; j<oc1[i].size(); ++j)
      |                 ~^~~~~~~~~~~~~~

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