Longest Arithmetic Increasing Subsequence

#User function Template for python3

class Solution:
    def lengthOfLongestAP(self, A, n):
        B=[{} for i in range(n)]
        B[0][A[0]]=1
        for i in range(1,n):
            for j in range(i):
                d=A[i]-A[j]
                if d in B[i]:
                    B[i][d]=max(B[i][d],1+B[j].get(d,1))
                else:
                    B[i][d]=B[j].get(d,1)+1
        ans=[]
        for i in B:
            if i:
                ans.append(max(i.values()))
            else:
                ans.append(0)
        return max(ans)


#{
#  Driver Code Starts
#Initial Template for Python 3

if __name__ == '__main__':
    tc = int(input())
    while tc > 0:
        n = int(input())
        A = list(map(int, input().split()))
        ob = Solution()
        ans = ob.lengthOfLongestAP(A, n)
        print(ans)
        tc -= 1

# } Driver Code Ends