995B - Suit and Tie - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<long long> a(2 * n);
    map<long long, int> Map;
    long long ans = 0;
    for (int i = 0; i < 2 * n; i++) {
        cin >> a[i];
        Map[a[i]] = i;
    }
    for (int i = 0; i < 2 * n; i += 2){
        for (int j = Map[a[i]]; a[j - 1] != a[i]; j--) {
            Map[a[j - 1]] = max(j , Map[a[j - 1]]);
            swap(a[j], a[j - 1]);
            ans++;
        }
    }

    cout << ans << endl;
    return 0;
}