chapter  20
Permutations
Pages 14

Let S be a set. By a permutation of S, we mean a bijection from S to S – thatis, a function from S to S that is both onto and 1-1. Permutations form a ratherpleasant and useful class of functions, and we shall study various aspects ofthem in this chapter. Example 20.1

(1) Let S = {1,2,3,4,5} and let f ,g : S→ S be defined as follows: f : 1→ 2,2→ 4,3→ 3,4→ 5,5→ 1, g : 1→ 3,2→ 4,3→ 1,4→ 2,5→ 4.