12 GenomicRangeQuery

/*------------------------------------------------------
A DNA sequence can be represented as a string consisting of the letters A, C, G and T, 
which correspond to the types of successive nucleotides in the sequence. 
Each nucleotide has an impact factor, which is an integer. 
Nucleotides of types A, C, G and T have impact factors of 1, 2, 3 and 4, respectively. 
You are going to answer several queries of the form: What is the minimal impact factor of nucleotides contained 
in a particular part of the given DNA sequence?

The DNA sequence is given as a non-empty string S = S[0]S[1]...S[N-1] consisting of N characters. 
There are M queries, which are given in non-empty arrays P and Q, each consisting of M integers. 
The K-th query (0 ≤ K < M) requires you to find the minimal impact factor of nucleotides contained in 
the DNA sequence between positions P[K] and Q[K] (inclusive).

Write a function that, given a non-empty string S consisting of N characters and two non-empty arrays P and 
Q consisting of M integers, returns an array consisting of M integers specifying the consecutive answers to all queries.

Result array should be returned as an array of integers.
------------------------------------------------------*/

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(S, P, Q) {
    // write your code in JavaScript (Node.js 8.9.4)
    let answers = [];
    let nucleoids = {
        A: [0],
        C: [0],
        G: [0],
        T: [0]
    }
    
    for (let i=0; i<S.length; i+=1) {
        if(i === 0) {
            nucleoids[S[i]][0] = 1;
            continue;
        }
        
        nucleoids.A[i] = nucleoids.A[i-1];
        nucleoids.C[i] = nucleoids.C[i-1];
        nucleoids.G[i] = nucleoids.G[i-1];
        nucleoids.T[i] = nucleoids.T[i-1];
        
        nucleoids[S[i]][i] += 1;
    }
    
    for (let i=0; i<P.length; i++) {
        let rangeStart = P[i];
        let rangeEnd = Q[i];
        
        if (nucleoids.A[rangeEnd] - nucleoids.A[rangeStart] > 0 || S[rangeStart] === 'A') {
            answers[i] = 1;
        } else if (nucleoids.C[rangeEnd] - nucleoids.C[rangeStart] > 0 || S[rangeStart] === 'C') {
            answers[i] = 2;
        }  else if (nucleoids.G[rangeEnd] - nucleoids.G[rangeStart] > 0 || S[rangeStart] === 'G') {
            answers[i] = 3;
        } else {
            answers[i] = 4;
        }
    }
    
    return answers;
}