Earliest Uniques in a Stream

Implement a data structure with the following methods:

• EarliestUnique(int[] nums) constructs a new instance with the given list of numbers.
• add(int num) adds num to the data structure.
• firstUnique() returns the first unique number. If there’s no unique number, return -1.

Constraints

• n ≤ 100,000 where n is the number of calls to add and firstUnique.

https://binarysearch.com/problems/Earliest-Uniques-in-a-Stream

Examples

Example 1

Input

• methods = ['constructor', 'add', 'earliestUnique', 'add', 'earliestUnique']
• arguments = [[[1, 2, 3]], [1], [], [2], []]

Output

• answer = [None, None, 2, None, 3]

Explanation

e = EarliestUnique([1, 2, 3])
e.add(1)
e.earliestUnique() == 2
e.add(2)
e.earliestUnique() == 3

Solution