LeetCode 1748 Sum of Unique Elements in Python | Easy Coding Tutorial for Beginners

Описание: Solve LeetCode 1748 "Sum of Unique Elements" in Python with this beginner-friendly coding tutorial! This problem asks you to find the sum of elements in an array that appear exactly once (e.g., nums = [1,2,3,2], return 4 because 1 and 3 are unique). We’ll use a list comprehension with `count()` to identify unique elements, and explore a more efficient solution using a frequency dictionary. Perfect for Python learners, coding beginners, or anyone prepping for coding interviews!

🔍 *What You'll Learn:*
Understanding LeetCode 1748’s requirements
Using `count()` to find unique elements in an array
Optimizing with a frequency dictionary for better performance
Testing with example cases

💻 *Code Used in This Video:*
class Solution(object):
def sumOfUnique(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
return sum(num for num in nums if nums.count(num) == 1)

Test cases
solution = Solution()

Test case 1: Mix of unique and duplicate elements
print(solution.sumOfUnique([1, 2, 3, 2])) # Output: 4
1 appears once, 2 appears twice, 3 appears once; Sum = 1 + 3 = 4

Test case 2: All elements are the same
print(solution.sumOfUnique([1, 1, 1, 1])) # Output: 0
No unique elements; Sum = 0

Test case 3: All elements are unique
print(solution.sumOfUnique([1, 2, 3, 4])) # Output: 10
All elements appear once; Sum = 1 + 2 + 3 + 4 = 10

Test case 4: Single element
print(solution.sumOfUnique([5])) # Output: 5
5 appears once; Sum = 5

Optimized: Using a frequency dictionary
from collections import Counter
class SolutionOptimized(object):
def sumOfUnique(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
freq = Counter(nums) # Count frequency of each number
return sum(num for num, count in freq.items() if count == 1)

solution_opt = SolutionOptimized()
print("\nOptimized solution:")
print(solution_opt.sumOfUnique([1, 2, 3, 2])) # Output: 4
print(solution_opt.sumOfUnique([1, 1, 1, 1])) # Output: 0

🌟 *Why Solve LeetCode 1748?*
This problem is a great introduction to array processing and frequency counting in Python, a common topic in coding interviews! The `count()` solution has a time complexity of O(n^2), but the optimized solution using a frequency dictionary reduces it to O(n) with O(n) space complexity. We’ll explore both methods to sum unique elements efficiently. Master this, and you’ll be ready for more advanced LeetCode challenges!

📚 *Who’s This For?*
Python beginners learning coding
Coding enthusiasts tackling LeetCode problems
Developers prepping for technical interviews

👍 Like, subscribe, and comment: What LeetCode problem should we solve next? Next up: More LeetCode array problems—stay tuned!

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