one-to-one correspondence?

Question

Let A:={1,2,3} and B:={4,5,6}. Define a function f:A->B that establishes a one-to-one correspondence between A and B.
thx in advance

Answer 1

Puzzling's answer is a good one; but there are many others, such as f(x) = 7 - x, which gives the one-to-one correspondence

1 -> 6
2 -> 5
3 -> 4

There are also four other distinct ways to map A into B in a one-to-one correspondence, but they will be a little trickier to describe as a function and each can be described by any of an infinite number of function rules.

Among them: f(x) = 4 + [x mod 3]. The x mod 3 gives a result between 0 and 3, including 0 but not 3, which is the positive remainder you get when you divide x by 3.

1 -> 5
2 -> 6
3 -> 4

Answer 2

How about the following:
f(x) = x + 3

1 --> 4
2 --> 5
3 --> 6