Compute Averages of Unique Numbers in Dictionary Lists

Q: Compute Averages of Unique Numbers in Dictionary Lists

This question evaluates data manipulation and aggregation skills, focusing on handling duplicate values within collections and computing numerical summaries of list data.

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Use PracHub's coding console to write, test, and debug your solutions in Python or JavaScript. View hints, test against sample inputs, and compare with official solutions.

Q: What difficulty level is this coding question?

This is a Medium difficulty Coding & Algorithms question, commonly asked during Onsite rounds at TikTok.

Q: What role is this question designed for?

This question is commonly asked for Data Scientist candidates at TikTok during technical interviews.

Question

##### Scenario

Python tech screen: given a dictionary mapping keys to numeric lists, e.g., {'a':[1,2,1],'b':[1,2,3]}, compute the average of each list after removing duplicates.

##### Question

Write Python code that takes any such dictionary and returns a new dictionary whose values are the average of the unique numbers in each original list.

##### Hints

Deduplicate each list (set or list(dict.fromkeys())), then take the mean.

PracHub · Accepted Answer

from typing import Dict, List

def average_of_unique(data: Dict[str, List[float]]) -> Dict[str, float]:
    result: Dict[str, float] = {}
    for key, values in data.items():
        unique_values = set(values)
        if unique_values:
            avg = sum(unique_values) / float(len(unique_values))
        else:
            avg = 0.0
        result[key] = float(avg)
    return result

For each key, convert its list to a set to remove duplicates, then compute the arithmetic mean of the unique values. If the list is empty, define the average as 0.0. Using a set provides O(n) processing per list and treats equal integers and floats as duplicates.

Quick Overview

Compute Averages of Unique Numbers in Dictionary Lists

Constraints

Solution

Explanation

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