Is Determine the Minimum Sum of a k-avoiding Array easy or hard?

LeetCode classifies this problem as Medium. The greedy idea is straightforward once you notice that pairs summing to k must be avoided, but recognizing the mathematical pattern that allows direct number generation requires some insight.

Determine the Minimum Sum of a k-avoiding Array Python/Java solution

Implement a greedy loop that keeps adding the smallest valid integer until n elements are chosen. In Python or Java, store selected numbers in a HashSet to check complements in O(1) time, or directly generate numbers from 1 to k/2 and then from k upward.

How to solve Determine the Minimum Sum of a k-avoiding Array in O(n)?

Iterate through positive integers and greedily pick the smallest valid number. Either check if k - x already exists using a hash set, or apply the mathematical observation that numbers up to k/2 can be taken safely and remaining numbers should start from k. Both methods build the array in linear time.

What is the best approach for Determine the Minimum Sum of a k-avoiding Array?

The best approach uses a greedy construction based on the observation that numbers x and k-x cannot both appear. Select numbers from 1 upward until reaching k/2, then continue from k if more elements are needed. This produces the minimum sum while maintaining the constraint in O(n) time and O(1) space.

Is Determine the Minimum Sum of a k-avoiding Array asked at Google/Amazon/Meta?

Greedy construction and complement‑avoidance patterns appear frequently in interviews at companies like Amazon, Google, and Meta. While this exact problem may vary, the underlying idea of avoiding pair sums and minimizing totals is a common interview theme.

What data structure is used in Determine the Minimum Sum of a k-avoiding Array?

The straightforward solution uses a hash set to track chosen numbers and quickly check whether the complement k - x already exists. The optimized mathematical approach removes the data structure entirely and generates numbers directly.

What is the time complexity of Determine the Minimum Sum of a k-avoiding Array?

Both common solutions run in O(n) time where n is the required array size. The greedy set-based method also uses O(n) extra space to track chosen values, while the direct math-based generation runs in O(1) space.

Description Hints 4 Solution Video 4:31

2829. Determine the Minimum Sum of a k-avoiding Array

Medium59.7% acceptance1 company

You are given two integers, n and k.

An array of distinct positive integers is called a k-avoiding array if there does not exist any pair of distinct elements that sum to k.

Return the minimum possible sum of a k-avoiding array of length n.

Example 1:

Input: n = 5, k = 4
Output: 18
Explanation: Consider the k-avoiding array [1,2,4,5,6], which has a sum of 18.
It can be proven that there is no k-avoiding array with a sum less than 18.

Example 2:

Input: n = 2, k = 6
Output: 3
Explanation: We can construct the array [1,2], which has a sum of 3.
It can be proven that there is no k-avoiding array with a sum less than 3.

Constraints:

1 <= n, k <= 50

Asked at 1 company

Infosys

Topics

Greedy Math

Hints open one at a time

Hint 1

Try to start with the smallest possible integers.

Hint 2

Check if the current number can be added to the array.

Hint 3

To check if the current number can be added, keep track of already added numbers in a set.

Hint 4

If the number i is added to the array, then i + k can not be added.

4:31

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1class Solution:
2    def minimumSum(self, n: int, k: int) -> int:
3        

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Input

5
4

Input

2
6

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