EasyNo. 1748
Sum of Unique Elements — LeetCode 1748 Python Solution
- Pattern
- Hash Map
- Topics
- Array, Hash Table, Counting
- Reading time
- 2 min
- Source
- leetcode.com
The problem
You are given an integer array nums. The unique elements of an array are the elements that appear exactly once in the array.
Example
- Input
- nums = [1,2,3,2]
- Output
- 4
- Explanation
- The unique elements are [1,3], and the sum is 4.
Python solution
class Solution:
def sumOfUnique(self, nums: List[int]) -> int:
cnt = Counter(nums)
return sum(x for x, v in cnt.items() if v == 1)Complexity
- Time
- O(n)
- Space · auxiliary
- O(n)
Pattern: Hash Map
Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 1748. Sum of Unique Elements is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Hash Table and Counting.
The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.
Related problems
| No. | Problem | Difficulty |
|---|---|---|
| 0169 | Majority Element | Easy |
| 0229 | Majority Element II | Medium |
| 0347 | Top K Frequent Elements | Medium |
| 0594 | Longest Harmonious Subsequence | Easy |
| 0621 | Task Scheduler | Medium |
| 0692 | Top K Frequent Words | Medium |
Frequently asked questions
- How hard is LeetCode 1748. Sum of Unique Elements?
LeetCode 1748. Sum of Unique Elements is rated Easy on LeetCode.
- What is the time complexity of LeetCode 1748. Sum of Unique Elements?
The Python solution on this page runs in O(n).
- What is the space complexity of LeetCode 1748. Sum of Unique Elements?
The Python solution on this page uses O(n) auxiliary space.
- What topics does LeetCode 1748. Sum of Unique Elements cover?
LeetCode 1748. Sum of Unique Elements is tagged Array, Hash Table and Counting on LeetCode.