mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    for _ in range(int(input())):
        N = int(input())
        P = [0] + list(map(int, input().split()))

        P_ori = P[:]

        ans = []
        ok = 1
        for p in range(1, N + 1):
            for i in range(1, N+1):
                if P[i] == p:
                    ii = i
                    break
            if ii == p:
                continue

            for i in range(ii - 1, p - 1, -1):
                j = i
                while P[j] == j + 1:
                    j -= 1
                    if j == p - 1:
                        break
                if j != p - 1 and j != i:
                    for jj in range(j, i):
                        ans.append(jj)
                        if P[jj] == jj or P[jj + 1] == jj + 1:
                            ok = 0
                        P[jj], P[jj + 1] = P[jj + 1], P[jj]
                ans.append(i)
                if P[i] == i or P[i + 1] == i + 1:
                    ok = -1
                P[i], P[i + 1] = P[i + 1], P[i]

        if ok == 1:
            print(len(ans))
            print(*ans)
            assert len(ans) <= N ** 2
        else:
            print(-1)

        if ok == 1:
            for i in ans:
                assert P_ori[i] != i and P_ori[i + 1] != i + 1
                P_ori[i], P_ori[i + 1] = P_ori[i + 1], P_ori[i]
            assert P_ori == list(range(N + 1))


if __name__ == '__main__':
    main()