How do you solve The k Strongest Values in an Array on LeetCode?

The k Strongest Values in an Array (LeetCode #1471) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n log n) time complexity and O(n) space complexity. Key insight: Understanding the concept of strength based on distance from the center is crucial.

What is the brute force solution for The k Strongest Values in an Array?

The brute force approach for The k Strongest Values in an Array is Brute Force, with O(n log n) time complexity and O(1) space complexity. The brute-force approach involves calculating the strength of each element in the array based on its distance from the center and then sorting the entire array to find the strongest k values. The optimal Optimal Solution approach improves this to O(n log n).

What algorithm or data structure is used to solve The k Strongest Values in an Array?

The k Strongest Values in an Array uses the following concepts: Array, Two Pointers, Sorting. The recommended patterns to study are: Sorting, Custom Comparator.

What are the interview tips for The k Strongest Values in an Array?

Always clarify the definition of 'strength' with the interviewer. Discuss your thought process and approach before jumping into coding. Consider edge cases, such as arrays with duplicate values or very small sizes.

What are common mistakes when solving The k Strongest Values in an Array?

Not correctly identifying the center value m after sorting. Confusing the sorting criteria when comparing strengths.

#1471

The k Strongest Values in an Array

Medium

ArrayTwo PointersSortingSortingCustom Comparator

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n log n)	O(n log n)
Space	O(1)	O(n)

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Intuition

Time O(n log n)Space O(n)

The optimal solution improves efficiency by directly sorting the array once and using a custom comparator to determine the strongest elements in a single pass, avoiding unnecessary sorting.

⚙️

Algorithm

3 steps

1Step 1: Sort the array to find the center value m.
2Step 2: Use a custom sort function to sort elements based on their strength and value.
3Step 3: Return the first k elements from the sorted array.

solution.py6 lines

1def getStrongest(arr, k):
2    arr.sort()
3    n = len(arr)
4    m = arr[(n - 1) // 2]
5    arr.sort(key=lambda x: (abs(x - m), x), reverse=True)
6    return arr[:k]

ℹ

Complexity note: The time complexity remains O(n log n) due to sorting, but we efficiently handle the selection of k elements. The space complexity is O(n) due to the storage of the sorted array.

1Understanding the concept of strength based on distance from the center is crucial.
2Sorting the array is a key step in both approaches, but the optimal solution leverages it more effectively.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.