## Description

https://leetcode.com/problems/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:8Explanation: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:-1Explanation:There is no number that occurs only once.

**Note:**

`1 <= A.length <= 2000`

`0 <= A[i] <= 1000`

## Explanation

Count, sort, and find out the result.

## Python Solution

```
class Solution:
def largestUniqueNumber(self, A: List[int]) -> int:
counter = {}
for num in A:
counter[num] = counter.get(num, 0) + 1
results = []
for key, value in counter.items():
if value == 1:
results.append(key)
if not results:
return -1
results = sorted(results)
return results[-1]
```

- Time Complexity: O(N)
- Space Complexity: O(Nlog(N))