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

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

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.

Input: ([],)

Expected Output: {}

Explanation: Empty input list returns an empty dictionary; nothing is printed.

Input: (["hello"],)

Expected Output: {"hello": 1}

Explanation: A single word appears once; only one word is available to print.

Input: (["x", "x", "x", "x"],)

Expected Output: {"x": 4}

Explanation: The same word repeated four times maps to a count of 4.

Input: (["red", "red", "blue", "green", "blue", "red", "yellow"],)

Expected Output: {"red": 3, "blue": 2, "green": 1, "yellow": 1}

Explanation: red=3, blue=2, then green and yellow tie at 1; the top-3 printed are red, blue, and one of the singletons.

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.

Quick Overview

This question evaluates proficiency in basic Python programming, string/text processing, frequency counting and sorting algorithms, reflecting core competencies for data manipulation tasks.