Character Frequency Analysis: A Python Problem Breakdown

The Problem

The HackerRank "Company Logo" problem asks you to find the three most frequent characters in a string, with alphabetical ordering as a tiebreaker. Here's one approach to solving it:

s = input()
slist = []
sdictionary = {}

for letter in s:
    slist.append(letter)

for letter in slist:
    if letter not in sdictionary.keys():
        sdictionary[letter] = 0
    if letter in sdictionary.keys():
        sdictionary[letter] = sdictionary[letter] + 1

sorted_items = sorted(sdictionary.items(), key=lambda x: (-x[1], x[0]))

for i in range(min(3, len(sorted_items))):
    key, value = sorted_items[i]
    print(f"{key} {value}")

How It Works

Step 1: Convert to list The code converts the input string to a list of characters. While strings are already iterable in Python, this makes the intent clear.

Step 2: Count frequencies Each character is checked against the dictionary. If it's new, it gets initialized to 0, then incremented. This ensures every character gets counted properly.

Step 3: Sort by criteria The sorting line does two things:

• -x[1] sorts by frequency in descending order

• x[0] sorts alphabetically for ties

Step 4: Print results Uses min(3, len(sorted_items)) to handle cases where there are fewer than 3 unique characters.

Why This Problem Matters

Character frequency analysis appears in:

• Text processing and analysis

• Compression algorithms

• Cryptography

• Data validation