Leetcode #2455: Average Value of Even Numbers That Are Divisible by Three
In this guide, we solve Leetcode #2455 Average Value of Even Numbers That Are Divisible by Three in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
Given an integer array nums of positive integers, return the average value of all even integers that are divisible by 3. Note that the average of n elements is the sum of the n elements divided by n and rounded down to the nearest integer.
Quick Facts
- Difficulty: Easy
- Premium: No
- Tags: Array, Math
Intuition
There is a mathematical invariant or formula that directly leads to the result.
Using math avoids unnecessary loops and reduces complexity.
Approach
Derive the formula or update rule, then compute the answer directly.
Handle edge cases like overflow or zero carefully.
Steps:
- Identify the math relationship.
- Compute the result with a loop or formula.
- Handle edge cases.
Example
Input: nums = [1,3,6,10,12,15]
Output: 9
Explanation: 6 and 12 are even numbers that are divisible by 3. (6 + 12) / 2 = 9.
Python Solution
class Solution:
def averageValue(self, nums: List[int]) -> int:
s = n = 0
for x in nums:
if x % 6 == 0:
s += x
n += 1
return 0 if n == 0 else s // n
Complexity
The time complexity is , where is the length of the array. The space complexity is .
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.