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Scale Ingredient Quantities

UpstartSoftware Engineer · Online Assessment
EasySoftware EngineerOnline AssessmentCoding & Algorithms

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This problem tests string parsing and manipulation, specifically isolating numeric prefixes from measurement units and descriptive text while maintaining the relative structure of ingredient lists.

Scaling Ingredients

You are building a feature for a recipe app that allows users to adjust serving sizes. You are given a list of strings, where each string represents an ingredient in the format: "[quantity] [unit] [name]".

Write a function scale_ingredients(ingredients, servings) that returns a new list of strings where the quantity of each ingredient has been multiplied by the servings factor.

Requirements:

  • The quantity will always be the first integer in the string.
  • The unit and name should remain unchanged.
  • If servings is 0, the output should reflect a quantity of 0 for all ingredients.
  • The function must preserve the original order of the input list.

Function Signature

def scale_ingredients(ingredients: list[str], servings: int) -> list[str]

Examples

Example 1: Input: ingredients = ["2 cups flour", "1 tbsp salt"], servings = 3 Output: ["6 cups flour", "3 tbsp salt"]

Example 2: Input: ingredients = ["10 grams sugar"], servings = 0 Output: ["0 grams sugar"]

Constraints

  • ingredients contains between 1 and 100 strings.
  • quantity will always be a positive integer in the input.
  • The format "[quantity] [unit] [name]" is guaranteed for every input string.
  • servings will be an integer between 0 and 1000.

Edge Cases

  • Consider inputs where servings is 0 or 1.
  • Ensure multi-word names (e.g., "extra virgin olive oil") are preserved correctly.

Hints

Hint 1

Use the string split method to isolate the first part of the string, which contains the quantity.

Hint 2

Convert the first substring into an integer, multiply it by the servings variable, and then join it back with the remainder of the original string.

Hint 3

The string method `split(maxsplit=1)` is useful for separating the quantity from the rest of the string description.

Follow-up questions

  • How would you modify your solution if the input format allowed for optional units (e.g., '2 eggs' instead of '2 units eggs')?
  • What if the input could contain floating-point quantities instead of integers?
  • How would you handle potential input validation errors if an ingredient string does not match the expected format?