Form a Triangle

problem id:-http://practice.geeksforgeeks.org/problems/form-a-triangle/0


code:--

#include<iostream>
#include<unordered_map>
using namespace std;
int fact(int num)
{
if(num==0||num==1)
return 1;
return num*fact(num-1);
}
int ncr(int n)
{
return fact(n)/(fact(n-3)*6);
}
int main()
{
int t;
cin>>t;
while(t--)
    {
    int n;
    cin>>n;
    int a[n];
for(int i=0;i<n;i++)
cin>>a[i];
if(n<3)
{
cout<<0<<'\n';
continue;
}
int count=0;
for(int i=0;i<n-1;i++)
{
unordered_map<int,bool> mymap;
for(int j=i+1;j<n;j++)
{
if(mymap.find(a[i])!=mymap.end())
   ++count;
else
   mymap[a[i]+a[j]]=true;
}
}
cout<<(ncr(n)-count)<<"\n";
    }
return 0;
}