Equal Pairs

You are given an array of integers ARR[]. Your task is to find the index of values that satisfy X + Y = Z + W, where X, Y, Z, and W are integer values in the array.

Example

If the given array ARR = {1,19,3,17,4,5,2,18} we can see that 1+19=2+18 and 1+19 = 3+17 but we will return indices which is lexicographically smaller so answer will be {0,1,2,3}.

Note:

You have to return the indices of the elements in the given order for example you have indices like i1,i2,i3,i4 so that i1 < i2 and i3 < i4, i1 < i3, i2 != i3 and i2 != i4.

If there is more than one solution, then return the pairs of indices that are lexicographically smallest.

Suppose you have two solutions S1 = i1, i2, i3, i4, and S2 = j1, j2, j3, j4 then S1 is lexicographically smaller than S2 if and only if i1 < j1 and if i1 = j1 then i2 < j2 and if i2=j2 then i3 < j3 and if i3=j3 then i4 < j4.

If no solution exists then return an ArrayList containing only -1.

Input format :

The first line of input contains an integer ‘T’ denoting the number of test cases.

The next ‘2*T’ lines represent the ‘T’ test cases.

The first line of each test case contains a single integer N denoting the size of the array.

The second line of each test case contains N space-separated integers denoting the array elements at various indices.

Output format :

For each test case, return an array list representing the indices that satisfy the given condition.

Note:

You don’t have to print anything; it has already been taken care of. Just implement the given function. 

Constraints:

1 <= T <= 100
1 <= N<= 100
1 ≤ ARR[I] ≤ 10^7

Time Limit: 1 sec