Submission #1189198

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Source Code Expand

#include <iostream>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;

int main()
{
    ios_base::sync_with_stdio(0);
    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; ++i)
        cin >> a[i];
    map<int, int> pos;
    for (int i = 0; i < n; ++i)
        pos[a[i]] = i;
    vector<int> b = a;
    sort(b.begin(), b.end());
    int odp = 0;
    for (int i = 0; i < n; ++i)
    {
        int x = i;
        int y = pos[b[i]];
        if ((y - x) % 2 == 0)
        {
            swap(pos[a[i]], pos[b[i]]);
            swap(a[x], a[y]);
        }
        else
        {
            swap(pos[a[i + 1]], pos[b[i]]);
            swap(a[i + 1], a[y]);
            swap(pos[a[i]], pos[a[i + 1]]);
            swap(a[i], a[i + 1]);
            ++odp;
        }
    }
    cout << odp;
    return 0;
}

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