What is the optimal time complexity of solving Counting Distinct Elements in an Array?

The optimized solution achieves a time complexity of O(n) by using sorting, mathematical shortcuts, or hash table lookups.

What is the auxiliary space complexity for Counting Distinct Elements in an Array?

The space complexity is O(1) since we only use a minimal/constant amount of extra memory for tracking variables (or auxiliary space if dynamic structures are allocated).

What are the typical edge cases we must handle in Counting Distinct Elements in an Array?

Key edge cases include empty collections, negative or large bounds causing integer overflow, arrays with only one element, or inputs where target criteria are not met.

How can we optimize the brute force approach for Counting Distinct Elements in an Array?

Brute force methods often inspect all possible combinations. We optimize this by sorting the input list to enable binary search, or tracking processed items in a set to avoid redundant nested loop lookups.

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Counting Distinct Elements in an Array

Learn how to solve the 'Counting Distinct Elements in an Array' problem. This detailed resource details brute force and optimized approaches.

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Problem Statement

Easy

Write a function count_distinct(arr) that takes a list of integers arr and returns the count of distinct (unique) elements in the array.

Constraints

•0 <= len(arr) <= 10^5
•-10^6 <= arr[i] <= 10^6

Examples

Example 1

Input

arr = [1, 2, 2, 3, 3, 3]

Output

Explanation

The distinct elements are 1, 2, and 3. Count = 3.

Example 2

Input

arr = [5, 5, 5, 5]

Output

Explanation

Only one distinct element: 5.

Example 3

Input

arr = [1, 2, 3, 4, 5]

Output

Explanation

All elements are distinct.

Need a Hint?

Use simple arithmetic operators (like modulo `%`, division `//`), conditional checks, or loops to inspect number properties.

Edge Cases to Watch

Empty list or null input variables
Single item lists/arrays
Extremely large input bounds causing integer or stack overflow

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