make all the numbers unique code example

Example 1: make all the numbers unique

Input: [3,2,1,2,1,7]
Output: 6
Explanation:  After 6 moves, the array could be [3, 4, 1, 2, 5, 7].
It can be shown with 5 or less moves that it is impossible for the array to have all unique values.

Example 2: make all the numbers unique

Input: [1,2,2]
Output: 1
Explanation:  After 1 move, the array could be [1, 2, 3].