find the value of ncr %1000000007

problem id:-http://practice.geeksforgeeks.org/problems/ncr/0

code:-

#include<iostream>
using namespace std;
int main()
{
int t;
cin>>t;
while(t--)
    {
    long long n,r;
    cin>>n>>r;
    if(n<r)
    {
cout<<0<<'\n';
continue;
}
int a[n+1]={0};// we use this array to save the nth row of pascal triangle and we keep overwriting it until we get our desired row
a[0]=1;
int rem=1000000007;
for(int i=1;i<=n;++i)
{
int j=i;
while(j>0)
{
a[j]=((a[j]%rem)+(a[j-1]%rem))%rem;
--j;
}
}
cout<<a[r]<<'\n';
    }
return 0;
}