1133. Largest Unique Number

Given an array of integers A , return the largest integer that only occurs once.

If no integer occurs once, return -1.

 

Example 1:

Input: 

[5,7,3,9,4,9,8,3,1]

Output: 

8

Explanation: 

The maximum integer in the array is 9 but it is repeated. The number 8 occurs only once, so it's the answer.

Example 2:

Input: 

[9,9,8,8]

Output: 

-1

Explanation: 

There is no number that occurs only once.

 

Note:

1. 1 <= A.length <= 2000
2. 0 <= A[i] <= 1000