Codility: GenomicRangeQuery Solution

1function solution(S, P, Q) {
2  const subtract = (y, x) => ({
3    A: y.A - x.A,
4    C: y.C - x.C,
5    G: y.G - x.G,
6    T: y.T - x.T,
7  })
8  const lowerBound = { A: 0, C: 0, G: 0, T: 0 }
9  const accumulatedNucleotideOccurence = { ...lowerBound }
10  const nucleotideOccurences = S.split("").map(c => {
11    accumulatedNucleotideOccurence[c]++
12    return { ...accumulatedNucleotideOccurence }
13  })
14  const res = P.map((p, i) =>
15    subtract(
16      nucleotideOccurences[Q[i]],
17      p === 0 ? lowerBound : nucleotideOccurences[p - 1]
18    )
19  ).map(nuOc => (nuOc.A ? 1 : nuOc.C ? 2 : nuOc.G ? 3 : 4))
20
21  return res
22}