Ramiro N. Cosa

Pounds to Kilograms - FreeCodeCamp Daily Challenge

2 min

Problem Statement

Given a weight in pounds as a number, return the string:

(lbs) pounds equals (kgs) kilograms.

Where:

  • (lbs) is replaced by the input number.
  • (kgs) is replaced by the value converted to kilograms, rounded and formatted to two decimals.
  • 1 pound equals 0.453592 kilograms.
  • If the input is 1, use “pound” instead of “pounds”.
  • If the converted value is 1, use “kilogram” instead of “kilograms”.

Initial Analysis

Understanding the Problem

The function receives a number representing a weight in pounds and must convert it to kilograms using the equivalence 1 pound = 0.453592 kg. The result should be a string formatted as:

(lbs) pounds equals (kgs) kilograms.

Decimal formatting and correct singular/plural usage must be handled.

Identified Test Cases

The following test cases ensure correct functionality:

  • Input: 1 → “1 pound equals 0.45 kilograms.” (singular)
  • Input: 0 → “0 pounds equals 0.00 kilograms.” (zero)
  • Input: 100 → “100 pounds equals 45.36 kilograms.” (large value)
  • Input: 2.5 → “2.5 pounds equals 1.13 kilograms.” (decimal)
  • Input: 2.20462 → “2.20462 pounds equals 1.00 kilogram.” (converted value equals 1)

Solution Development

Approach

The conversion is done by multiplying the value in pounds by the factor 0.453592 to obtain the weight in kilograms. The result is rounded and formatted to two decimals. Singular or plural is used as appropriate.

Conversion Diagram

flowchart TB
  A[Pounds] -- x 0.453592 --> B[Kilograms]
  B -- Round to 2 decimals --> C[Result]
  C -- Format string --> D[Final output]

Implementation

function poundsToKilograms(lbs) {
  const kgs = lbs * 0.453592;
  const roundedKgs = kgs.toFixed(2);
  const poundWord = lbs === 1 ? "pound" : "pounds";
  const kilogramWord = parseFloat(roundedKgs) === 1 ? "kilogram" : "kilograms";
  return `${lbs} ${poundWord} equals ${roundedKgs} ${kilogramWord}.`;
}

Complexity Analysis

Time complexity: O(1) (constant operations)

Space complexity: O(1) (no additional structures)

Edge Cases and Considerations

  • Input equal to 0: “0 pounds equals 0.00 kilograms.”
  • Input equal to 1: “1 pound equals … kilograms.”
  • Converted value equal to 1: ”… equals … kilogram.”
  • Decimal and large numbers: correct formatting and rounding.
  • The result should always show two decimals.

Reflections and Learnings

Applied concepts:

  • Unit conversion and number formatting.
  • Conditionals for singular/plural.
  • Rounding and decimal formatting.

Possible improvements: The function is optimal in performance. Readability could be improved or the logic reused in other contexts.

Resources and References

freecodecamp daily-challenge