#include "shoes.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
ll inversion_count(vector<int> s)
{
int n = s.size();
if (n<=1)
return 0;
vector<int> l;
vector<int> r;
for (int i=0; i<(n/2); i++)
l.push_back(s[i]);
for (int i=n/2; i<n; i++)
r.push_back(s[i]);
ll k = 0;
ll m = 0;
ll ans = inversion_count(l) + inversion_count(r);
sort(l.begin(), l.end());
sort(r.begin(), r.end());
while ((k<(n/2)) and (m<((n+1)/2)))
{
if (l[k] > r[m])
{
ll add = (n/2) - k;
ans += add;
m++;
}
else
k++;
}
return ans;
}
long long count_swaps(std::vector<int> s) {
int n = (s.size())/2;
vector<int> left_shoe_count(n+1, 0);
vector<int> right_shoe_count(n+1, 0);
map<pii, int> renumber;
vector<int> new_s(2*n);
int c = 1;
for (int i=0; i<(2*n); i++)
if (s[i] < 0)
{
left_shoe_count[0-s[i]]++;
renumber[{0-s[i], left_shoe_count[0-s[i]]}] = c;
new_s[i] = c;
c+=2;
}
for (int i=0; i<(2*n); i++)
if (s[i] > 0)
{
right_shoe_count[s[i]]++;
new_s[i] = 1 + renumber[{s[i], right_shoe_count[s[i]]}];
}
return inversion_count(new_s);
}
