#include<bits/stdc++.h>
#define N 10000007
#define ll long long
using namespace std;
int a[N], tree[N];
int query(int indx)
{
int sum = 0;
while(indx > 0)
{
sum += tree[indx];
indx = indx - (indx & (-indx));
}
return sum;
}
void update(int indx, int value, int n)
{
while(indx <= n)
{
tree[indx] += value;
indx = indx + (indx & (-indx));
}
}
void convert(int n)
{
int temp[n];
for(int i=0; i<n; i++)
temp[i] = a[i];
sort(temp, temp+n);
for(int i=0; i<n; i++)
{
int low = 0, heights = n-1, m;
while(low <= heights)
{
m = (low + heights)/2;
if(a[i] == temp[m])
break;
else if(a[i] < temp[m])
heights = m-1;
else
low = m+1;
}
a[i] = m+1;
}
}
int invcnt(int n)
{
convert(n);
int cnt = 0;
for(int i=n-1; i>=0; i--)
{
cnt += query(a[i] - 1);
update(a[i], 1, n);
}
return cnt;
}
int main()
{
int n;
cin >> n;
for(int i=0; i<n; i++)
cin >> a[i];
cout << "Number of Inversion :: " << invcnt(n) << "\n";
return 0;
}
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