# LeetCode 1748. Sum of Unique Elements

## 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: 4
Explanation: The unique elements are [1,3], and the sum is 4.
```

Example 2:

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

Example 3:

```Input: nums = [1,2,3,4,5]
Output: 15
Explanation: 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)