"""
Largest Unique Number
    Given an integer array nums, return the largest
    integer that occurs exactly once. If no integer
    occurs once, return -1.

Example 1
    Input: nums = [5, 7, 3, 9, 4, 9, 8, 3, 1]
    Output: 8

    Explanation:
    The maximum value 9 appears more than once.
    The largest value that appears exactly once
    is 8.

Example 2
    Input: nums = [9, 9, 8, 8]
    Output: -1

    Explanation:
    No number appears exactly once.

Constraints
    1 <= len(nums) <= 2000
    0 <= nums[i] <= 1000

Expected Complexity
    Time  O(n)
    Space O(n)
"""


def solution(nums):
    pass


print("Largest Unique Number", end=" ")
assert solution([5, 7, 3, 9, 4, 9, 8, 3, 1]) == 8, "example 1 failed"
assert solution([9, 9, 8, 8]) == -1, "example 2 failed"
assert solution([42]) == 42, "single element failed"
assert solution([1, 2, 2, 3, 3, 4]) == 4, "largest unique selection failed"
print("OK")