Section 1.4: Composition of Functions

Solution
One-one function from \(\{1, 2, 3\}\) to itself is simply a permutation of three symbols \(1, 2, 3\).
Therefore, total number of one-one maps from \(\{1, 2, 3\}\) to itself is same as total number of permutations on three symbols \(1, 2, 3\) which is \(3! = 6\).