def heap(n,A):

    if n == 1:

        print A

    else:

        heap(n-1,A)

        for i in range(0,n-1):

            if n%2 == 0:

                x = A[i]

                A[i] = A[n-1]

                A[n-1] = x

            else:

                x = A[0]

                A[0] = A[n-1]

                A[n-1] = x

            heap(n-1,A)

heap(5,[1,2,3,4,5])

​