🦄 Feather Sort: By Length then Lexicographic

Difficulty: Beginner Tags: sorting, strings, multi-key sorting Series: CS 101

Problem

Sort a list of words with a twist: first by length (shortest to longest), then alphabetically if words have the same length!

This is called multi-level sorting or sorting by multiple keys.

Input

data = list[str]  # List of words to sort

Output

list[str]  # Sorted list (new list, don't modify original)

Constraints

• List can have up to 100,000 words
• All words contain only lowercase letters (a-z)

Examples

Example 1: Basic Sorting

Input:  ['aa', 'b', 'ab']
Output: ['b', 'aa', 'ab']

Step-by-step: 1. Sort by length first: - 'b' has length 1 - 'aa' has length 2 - 'ab' has length 2

1. For same-length words, sort alphabetically:
2. Length 1: 'b' (only one word)

3. Length 2: 'aa' comes before 'ab' alphabetically

4. Result: ['b', 'aa', 'ab']

Example 2: Multiple Ties

Input:  ['a', 'b', 'aa', 'ab']
Output: ['a', 'b', 'aa', 'ab']

Why? - Length 1: 'a' and 'b' → alphabetically: 'a', 'b' - Length 2: 'aa' and 'ab' → alphabetically: 'aa', 'ab'

Example 3: All Same Length

Input:  ['dog', 'cat', 'bat', 'ant']
Output: ['ant', 'bat', 'cat', 'dog']

All words have length 3, so they're sorted purely alphabetically.

Example 4: All Different Lengths

Input:  ['apple', 'cat', 'banana', 'a']
Output: ['a', 'cat', 'apple', 'banana']

Lengths: 1, 3, 5, 6 → automatically sorted by length.