coding challenge solution with a hidden bug

byMR

June 21, 2023

Recently I took a coding challenge on turing. The question was :

You will be given a string list(ops) as input.

If its an integer you have to keep a record of it
If it’s a character ‘C’, you have to remove the last recorded element
If it’s a character ‘D’, you have to double the last element and record it
If it’s a character ‘+’, you have to add the last two elements and record it
Return the final sum of records.

Example input,
ops = ["5", "2", "C", "D", "+"]
output = 30

I was able to write the code, however it did not pass. In retrospective, I am just trying to find what went wrong. Please find my code below:

def score_calculator
    scores = []
    ops.each do |rec|
        scores << rec.to_i if rec.is_a?(Integer)
        scores << scores.last(2).sum if rec == '+'
        scores << (scores.last.to_i * 2) if rec = 'D'
        scores.pop if rec == 'C'
    end
    return scores.sum
end

>Solution :

Here’s how you could still run your code with a little improvement..

def score_calculator
    scores = []
    ops.each do |rec|
        scores << rec.to_i if rec.match?(/[[:digit:]]/)
        scores << scores.last(2).sum if rec == '+'
        scores << (scores.last.to_i * 2) if rec == 'D'
        scores.pop if rec == 'C'
    end
    return scores.sum
end