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Implement string-based rounding without floats

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EasyMachine Learning EngineerTechnical ScreenCoding & Algorithms

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This question evaluates proficiency in string-based numeric processing, arbitrary-precision arithmetic concepts, precise rounding rules including deterministic tie-breaking, and handling of sign and decimal edge cases, and falls under the Coding & Algorithms domain.

Coding

You are not allowed to parse the input into a built-in floating type (to avoid overflow and precision issues). Work directly on strings.

1) Implement round(s) from scratch

Given a string s representing a decimal number, return a string representing the value rounded to the nearest integer.

  • s may include an optional sign (+/-) and an optional decimal point.
  • Examples of tricky inputs you must handle:
  • "-.2" (equivalent to -0.2)
  • "2." (equivalent to 2.0)
  • Very long integer parts that would overflow float()

Clarify and implement a deterministic tie-breaking rule (e.g., exactly .5 cases).

2) Round a numeric string s to a given precision p

Given two strings:

  • s: a decimal number as a string
  • p: a positive decimal precision as a string

Return s rounded to the nearest multiple of p (as a string).

Examples:

  • s = "12567", p = "100" → return "12600"
  • s = "1234.678", p = "0.1" → return "1234.7"

Assume p is a power of 10 (e.g., 1000, 0.01, 0.1). Specify how you format the output (e.g., whether to keep trailing zeros).