## Description

https://leetcode.com/problems/sum-of-unique-elements/

You are given an integer array `nums`

. The unique elements of an array are the elements that appear **exactly once** in the array.

Return *the sum of all the unique elements of *

`nums`

.**Example 1:**

Input:nums = [1,2,3,2]Output:4Explanation:The unique elements are [1,3], and the sum is 4.

**Example 2:**

Input:nums = [1,1,1,1,1]Output:0Explanation:There are no unique elements, and the sum is 0.

**Example 3:**

Input:nums = [1,2,3,4,5]Output:15Explanation:The unique elements are [1,2,3,4,5], and the sum is 15.

**Constraints:**

`1 <= nums.length <= 100`

`1 <= nums[i] <= 100`

## Explanation

Count first then add only unique numbers to the sum.

## Python Solution

```
class Solution:
def sumOfUnique(self, nums: List[int]) -> int:
visited = {}
sum = 0
for num in nums:
visited[num] = visited.get(num, 0) + 1
for key, value in visited.items():
if value == 1:
sum += key
return sum
```

- Time Complexity: O(N)
- Space Complexity: O(1)