factCheck.ts

const FACTS = [
  'm = 3.28 ft',
  'ft = 12 in',
  'hr = 60 min',
  'min = 60 sec',
]

const QUERY = '2 m = ? in'

const CORRECT_ANSWER = 78.72

// implement function answerQuery(query: string, facts: string[]): number
// i.e. find '?' value

// example solution

type Dict = Map<string, [string, number]>

function parseStatement(statement: string) {
  const [xa, yb] = statement.split(/\s*=\s*/)
  let [x, a] = xa.split(/\s+/)
  let [y, b] = yb.split(/\s+/)

  if (!a) {
    a = x
    x = '1'
  }

  if (!b) {
    b = y
    y = '1'
  }

  return {
    x: Number(x),
    a,
    y: Number(y),
    b,
  }
}

// m = 3.28 ft
function parseFacts(facts: string[]) {
  const dict: Dict = new Map()

  facts.forEach(fact => {
    const { x, a, y, b } = parseStatement(fact)
    dict.set(a, [b, y / x])
  })

  return dict
}

// 2 m = ? in
function answerQuery(query: string, facts: string[]): number {
  const dict = parseFacts(facts)

  const { x, a, y, b } = parseStatement(query)

  // let's assume y should always be '?'
  if (!Number.isNaN(y)) {
    throw Error('Unsupported query format')
  }

  let finalRatio = 1
  let finalUnit = a

  while (finalUnit !== b) {
    const [unit, ratio] = dict.get(finalUnit) || []

    if (!unit) {
      throw Error('Not enough facts')
    }

    finalRatio *= (ratio || 1)
    finalUnit = unit
  }

  return x * finalRatio
}

const answer = answerQuery(QUERY, FACTS)

console.log(answer === CORRECT_ANSWER ? 'ok' : 'fail')