Submission #3231088

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Source Code Expand

#include <iostream>
#include <vector>
using namespace std;
typedef long long ll;
string S;
vector<vector<int>> v(26);
int A[26] = {0},id[26] = {0};

ll merge_count(vector<ll> &a){
	int n = a.size();
	if(n<=1) return 0;
	ll cnt = 0;
	vector<ll> b(a.begin(),a.begin() + n/2);
	vector<ll> c(a.begin() + n/2, a.end());
	cnt += merge_count(b);
	cnt += merge_count(c);
	int ai = 0,bi = 0,ci = 0;
	while(ai<n){
		if(bi<b.size() && (ci == c.size() || b[bi] <= c[ci])){
			a[ai++] = b[bi++];
		}else{
			cnt += n/2 - bi;
			a[ai++] = c[ci++];
		}
	}
	return cnt;
}


int main(){
	cin >> S;
	string T = "";
	int N = S.size();
	for(int i=0;i<N;i++){
		int t = S[i]-'a';
		T = T + S[N-i-1];
		A[t]++;
		v[t].push_back(-1);
	}
	int count = 0;
	for(int i=0;i<26;i++){
		if(A[i]%2==1) count++;
	}
	if(count>=2){
		cout << -1 << endl;
		return 0;
	}
	vector<ll> L,R;
	int l = 0;
	for(int i=0;i<N;i++){
		int c = S[i]-'a';
		if(A[c]%2==1) L.push_back(N/2);
		else{
			if(id[c]*2<v[c].size()){
				L.push_back(l);
				v[c][id[c]] = l;
				l++;
				id[c]++;
			}else{
				int t = v[c].size()-id[c]-1;
				L.push_back(N-v[c][t]-1);
				id[c]++;
			}
		}
	}
	l = 0;
	for(int i=0;i<26;i++) id[i] = 0;
	for(int i=0;i<N;i++){
		int c = T[i]-'a';
		if(A[c]%2==1) R.push_back(N/2);
		else{
			if(id[c]*2<v[c].size()){
				R.push_back(l);
				v[c][id[c]] = l;
				l++;
				id[c]++;
			}else{
				int t = v[c].size()-id[c]-1;
				R.push_back(N-v[c][t]-1);
				id[c]++;
			}
		}
	}
/*	cout << S << " " << T << endl;
	for(int i=0;i<N;i++){
		cout << L[i] << (i!=N-1? " ":"\n");
	}
	for(int i=0;i<N;i++){
		cout << R[i] << (i!=N-1? " ":"\n");
	}
*/	cout << min(merge_count(L),merge_count(R)) << endl;
}

Submission Info

Judge Result