String Parsing Without Libraries | Dataford Interview Questions

Tell me about a time you built a solution that parses strings without relying on fancy libraries, and how you reasoned about runtime and edge cases.

Implement parse_fields(text) using only basic string operations. Parse comma-separated fields, allowing quoted fields to contain commas and backslash escapes. Return a list of decoded fields, or None for malformed input. Preserve spaces and empty fields.

Input is a string, and output is list[str] | None. A quote may begin only at a field boundary; after a closing quote, only a comma or end of input is valid.

Constraints

0 <= len(text) <= 5000
Input contains ordinary characters, commas, double quotes, and backslashes
Backslash escapes the immediately following character
A quote may begin only at the start of a field
Malformed input must return None

Function Signature

def parse_fields(text):

Your question is String Parsing Without Libraries. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Tell me about a time you built a solution that parses strings without relying on fancy libraries, and how you reasoned about runtime and edge cases.

Input is a string, and output is list[str] | None. A quote may begin only at a field boundary; after a closing quote, only a comma or end of input is valid.

Constraints

0 <= len(text) <= 5000
Input contains ordinary characters, commas, double quotes, and backslashes
Backslash escapes the immediately following character
A quote may begin only at the start of a field
Malformed input must return None

Function Signature

def parse_fields(text):

Your question is String Parsing Without Libraries. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.