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)

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