Submission #529390

#	Time	Username	Problem	Language	Result	Execution time	Memory
529390		penguinhacker	Ekoeko (COCI21_ekoeko)	C++14	110 / 110	10 ms	2744 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 r=0;
	for (++i; i; i-=i&-i)
		r+=ft[i];
	return r;
}

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	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;
	return 0;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:44:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   44 |   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