A13313 | Even Subset Sum Problem

You are given an array $a$ consisting of $n$ positive integers. Find a non-empty subset of its elements such that their sum is even (i.e. divisible by $2$ ) or determine that there is no such subset.

Both the given array and required subset may contain equal values.

The first line contains a single integer $t$ ( $1 \leq t \leq 100$ ), number of test cases to solve. Descriptions of $t$ test cases follow.

A description of each test case consists of two lines. The first line contains a single integer $n$ ( $1 \leq n \leq 100$ ), length of array $a$ .

The second line contains $n$ integers $a_1, a_2, \ldots, a_n$ ( $1 \leq a_i \leq 100$ ), elements of $a$ . The given array $a$ can contain equal values (duplicates).

For each test case output $-1$ if there is no such subset of elements. Otherwise output positive integer $k$ , number of elements in the required subset. Then output $k$ distinct integers ( $1 \leq p_i \leq n$ ), indexes of the chosen elements. If there are multiple solutions output any of them.