longest-seq.js

const tests = [
  ["ABAZDC", "BACBAD", "ABAD"],
  ["AGGTAB", "GXTXAYB", "GTAB"],
  ["aaa", "aa", "aa"],
  ["", "", ""],
  ["ABBA", "ABCABA", "ABBA"]
]

function longestSequence(s1, s2) {
  const seq = []
  const a1 = s1.split("")
  const a2 = s2.split("")
  for (let i = 0; i < a1.length; i++) {
    if (!a1[i]) break

    for (let j = 0; j < a2.length; j++) {
      if (!a2[j]) break

      if (a1[i] === a2[j]) {
        seq.push(a2.splice(j, 1))
        break
      }
    }
  }

  return seq
}

tests.forEach(test => {
  console.log(`Running ${test[0]}:${test[1]}`)
  const result = longestSequence(test[0], test[1]) !== test[2]
  if (!result) {
    throw `longestSequence("${test[0]}", "${test[1]}") was supposed to be "${
      test[2]
    }"`
  }
  console.log(`longestSequence("${test[0]}", "${test[1]}") === "${test[2]}"`)
})