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Python BasicsEasy
Finding the frequency of elements in an array
Learn how to solve the 'Finding the frequency of elements in an array' problem. This detailed resource details brute force and optimized approaches.
Problem Statement
Easy
Write a function frequency(arr) that takes a list of integers arr and returns a dictionary where each key is an element from the array and each value is the number of times that element appears. Return the dictionary sorted by keys in ascending order.
Constraints
- •0 <= len(arr) <= 10^5
- •-10^6 <= arr[i] <= 10^6
Examples
Example 1
Input
arr = [1, 2, 2, 3, 3, 3]
Output
{1: 1, 2: 2, 3: 3}Explanation
1 appears once, 2 appears twice, 3 appears three times.
Example 2
Input
arr = [5, 5, 5, 5]
Output
{5: 4}Explanation
5 appears four times.
Example 3
Input
arr = [4, 1, 2, 1, 4]
Output
{1: 2, 2: 1, 4: 2}Explanation
1 appears 2 times, 2 appears 1 time, 4 appears 2 times.
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
Ready to Solve?
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