Codetail is where developers practice with sandboxed execution, AI code review, and problems pulled from real production patterns, not toy exercises.
A search analytics pipeline counts how often each term appears in a query log before ranking results by popularity.
"Go" and "go" are different wordsFunction signature
Example 1
Input: words = ["go", "python", "go", "rust"]
Output: {"go": 2, "python": 1, "rust": 1}
"go" appears twice, others once.
Test Cases
Test 1
Input: ["go","python","go","rust"]
Expected: {"go":2,"python":1,"rust":1}
Test 2
Input: []
Expected: {}
Test 3
Input: ["django"]
Expected: {"django":1}
Test 4
Input: ["a","b","a","c","b","a"]
Expected: {"a":3,"b":2,"c":1}
Test 5
Input: ["x","y","z"]
Expected: {"x":1,"y":1,"z":1}
Test 6
Input: ["ok","ok"]
Expected: {"ok":2}
Codetail brings AI review, sandboxed execution, structured paths and progress tracking into one place, built around how developers actually practice.
Django, FastAPI, SQL and Go submissions get scored against a real rubric and reviewed by AI, not just checked for pass or fail.
Clean structure and clear naming, but the empty-list edge case is not explicitly handled.
Write and fix Python in an isolated subprocess. Every test case runs for real against your code, no simulated output.
$ python3 -m pytest main.py
$
Problems organized by stack and difficulty, from fundamentals to production patterns, so you always know what's next.
Python Fundamentals
8 of 12 problems
Django ORM Patterns
2 of 10 problems
SQL Window Functions
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