The number of swaps required in selection sort
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll a[111111], tmp[111111], ans;
void merge_sort(ll a[], ll b[], ll lo, ll hi)
{
ll i, j, k;
if (lo >= hi)
return;
ll mid = (lo + hi) / 2;
merge_sort(a, b, lo, mid);
merge_sort(a, b, mid + 1, hi);
i = lo;
j = mid + 1;
for (k = lo; k <= hi; k++)
if (j > hi)
b[k] = a[i++];
else if (i > mid)
b[k] = a[j++];
else if (a[i] <= a[j])
b[k] = a[i++];
else
{
b[k] = a[j++];
ans += mid - i + 1;
}
for (i = lo; i <= hi; i++)
a[i] = b[i];
}
int main(void)
{
ll t;
scanf("%lld", &t);
while (t--)
{
ll n, i;
scanf("%lld", &n);
for (i = 1; i <= n; i++)
scanf("%lld", &a[i]);
ans = 0;
merge_sort(a, tmp, 1, n);
printf("%lld\n", ans);
}
return 0;
}