SUMTRAIN-Getting runtime error

general
1

I have been working on the [SUMTRAIN][1] problem. I used the approach mentioned [here][2]. Following is the code that I have come up with.

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int t,n,a,b,e,f,g;
	cin>>t;
	while(t--)
	{
		cin>>n;
		int arr[n][n];
		for(a=0;a<n;a++)
			for(b=0;b<=a;b++)
				cin>>arr[a][b];
		if(n==1)
			cout<<arr[0][0]<<endl;
		else if(n==2)
		{
			if(arr[1][0]>arr[1][1])
				cout<<arr[0][0]+arr[1][0]<<endl;
			else
				cout<<arr[0][0]+arr[1][1]<<endl;
		}
		else
		{

			while(n--)
			{

				int d[(n-1)*2];
				for(e=0;e<((n-1)*2);e++)
				{
					d[e]=arr[n-1][f]+arr[n-2][e-f];
					if(e%2==0)
						f++;
				}
				sort(d,d+(sizeof(d)/sizeof(int)));
				reverse(d,d+(sizeof(d)/sizeof(int)));
				for(g=0;g<(n-1);g++)
					arr[n-2][g]=d[g];

				cout<<arr[0][0]<<endl;
			}
		}

	}


	return 0;
}

I am not getting solutions for any n>2. What could be the problem?
[1]: http://www.codechef.com/problems/SUMTRIAN/
[2]: http://discuss.codechef.com/questions/4557/need-guidance-in-sums-in-triangle-problem