longest-seq.ts

function longestSeq(arr, of) {
  let lengths = {}
  let max = 0
  arr.forEach(n => {
    if (lengths[n - of]) {
      lengths[n] = lengths[n - of] + 1
      delete lengths[n - of]
    } else {
      lengths[n] = 1
    }
    if (lengths[n] > max) {
      max = lengths[n]
    }
  })
  return max
}