Count Word Frequency and Print Top Three Words
Company: PayPal
Role: Data Scientist
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Onsite
##### Scenario
First-round Python coding screening
##### Question
Using only basic Python, write a function that receives a list of strings and returns a dictionary mapping each unique word to its frequency. Then print the three most frequent words in descending order.
##### Hints
Build dict with a for-loop; sort by value to get top-3.
Quick Answer: This question evaluates proficiency in basic Python programming, string/text processing, frequency counting and sorting algorithms, reflecting core competencies for data manipulation tasks.
Using only basic Python (no imports, no Counter), write a function that receives a list of word strings and returns a dictionary mapping each unique word to the number of times it appears. As a side effect, print the three most frequent words in descending order of frequency (one per line, as `word count`).
The function's RETURN VALUE is the frequency dictionary; that is what is graded. Build the dictionary with a simple for-loop, then sort the items by count to find the top three.
Example:
Input: ["apple", "banana", "apple", "cherry", "banana", "apple"]
Returns: {"apple": 3, "banana": 2, "cherry": 1}
Prints:
apple 3
banana 2
cherry 1
Constraints
- Use only basic Python — no `collections.Counter`, no external libraries.
- Words are compared exactly as given (case-sensitive, no normalization).
- The list may be empty, in which case return an empty dict.
- If there are fewer than three unique words, print only the words that exist.
- The returned dictionary maps every unique word to its exact count.
Examples
Input: (["apple", "banana", "apple", "cherry", "banana", "apple"],)
Expected Output: {"apple": 3, "banana": 2, "cherry": 1}
Explanation: apple appears 3 times, banana 2, cherry 1. The dict captures all counts; the top-3 printed are apple, banana, cherry.
Input: (["a", "b", "c", "d"],)
Expected Output: {"a": 1, "b": 1, "c": 1, "d": 1}
Explanation: All four words are unique, each with frequency 1.
Hints
- Initialize an empty dict and loop over the words: if the word is already a key, increment its value; otherwise set it to 1.
- Use `sorted(freq.items(), key=lambda kv: kv[1], reverse=True)` to order the words by frequency from highest to lowest.
- Slice the sorted list with `[:3]` to take only the top three, then print each `word count` pair.