Discussion on: A coding interview question asked at Google

[Firee80]

This solution allows n-amount of inputs and uses Set to check all items are the same.

function checkEquivalentKeypresses(...keyPressLines) {
  const keyPressArrays = keyPressLines.map(keyPressLine => keyPressLine.split(','))
  const keyPressArraysWithoutBackspace = keyPressArrays.map(array =>
    array.reduce((result, letter) => letter === '-B' ? [...result].slice(0, -1) : [...result, letter], []))
  const keyPressLinesWithoutBackspace = keyPressArraysWithoutBackspace.map(array => array.join(''))  
  return keyPressLines.length > 1 ? (new Set(keyPressLinesWithoutBackspace)).size === 1 : false  
}

console.log(checkEquivalentKeypresses(...['a,b,c,d', 'a,b,c,c,-B,d'])) // true
console.log(checkEquivalentKeypresses(...['-B,-B,-B,c,c', 'c,c'])) // true
console.log(checkEquivalentKeypresses(...['', 'a,-B,-B,a,-B,a,b,c,c,c,d'])) // false

[elisabethgross]

Nice!

[Firee80]

made the function to support also other data types of input..
changed naming and simplified return statement (new Set() is not ran if result.length > 1 fails first).

function checkEquivalentKeypresses(...lines) {
  const linesSplit = lines.some(line => typeof(line) !== 'string') ? [] : lines.map(line => line.split(','))
  const linesNoBackspace = linesSplit.map(lineArray =>
    lineArray.reduce((result, key) => key === '-B' ? [...result].slice(0, -1) : [...result, key], []))
  const result = linesNoBackspace.map(array => array.join(''))
  return result.length > 1 && (new Set(result)).size === 1  
}

console.log(checkEquivalentKeypresses(...['a,b,c,d', 'a,b,c,c,-B,d'])) // true
console.log(checkEquivalentKeypresses(...['-B,-B,-B,c,c', 'c,c'])) // true
console.log(checkEquivalentKeypresses(...['', 'a,-B,-B,a,-B,a,b,c,c,c,d'])) // false
console.log(checkEquivalentKeypresses(NaN,{})) // false
console.log(checkEquivalentKeypresses('a,b,c','a,b,c,d,-B')) // true

[David Madden]

Doesn't Set remove duplicates?

[Firee80]

yes.. that is why end result size should be 1
[1,1,1] => [1]
the code checks first that the initial array has more than 1 input so
[1] => [1]
would fail on the first length check