java codility training Genomic-range-query

Question

The task is:

A non-empty zero-indexed string S is given. String S consists of N characters from the set of upper-case English letters A, C, G, T.

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Answer 1

In ruby (100/100)

def interval_sum x,y,p
    p[y+1] - p[x]
end

def solution(s,p,q)

    #Hash of arrays with prefix sums

    p_sums = {}
    respuesta = []


    %w(A C G T).each do |letter|
        p_sums[letter] = Array.new s.size+1, 0
    end 

    (0...s.size).each do |count|
        %w(A C G T).each do |letter|
            p_sums[letter][count+1] = p_sums[letter][count] 
        end if count > 0

        case s[count]
        when 'A'
            p_sums['A'][count+1] += 1
        when 'C'
            p_sums['C'][count+1] += 1
        when 'G'
            p_sums['G'][count+1] += 1
        when 'T'
            p_sums['T'][count+1] += 1
        end 

    end




    (0...p.size).each do |count|


        x = p[count]
        y = q[count]


        if interval_sum(x, y, p_sums['A']) > 0 then
            respuesta << 1
            next
        end 

        if interval_sum(x, y, p_sums['C']) > 0 then
            respuesta << 2
            next
        end 

        if interval_sum(x, y, p_sums['G']) > 0 then
            respuesta << 3
            next
        end 

        if interval_sum(x, y, p_sums['T']) > 0 then
            respuesta << 4
            next
        end 

    end

    respuesta

end