CODEWITHSUNDEEP
ruby
user815693
user815693

Reputation: 516

Sum Number String and Integer and Keep the zeroes in the beginning of the string

How to sum str and num in Ruby?
And return string again.
In a way to preserve the zeros in the beginning of the string.

Example:

str = "001"  
num = 3

Expected result: 

str + num #=> "004"

Upvotes: 0

Views: 282

Answers (3)

Cary Swoveland
Cary Swoveland

Reputation: 110735

If you don't mind modifying str, you could do this:

3.times { str.next! }
str #=> "004"

If you don't want to modify str, operate on str.dup.

Alternatively:

3.times.reduce(str) { |s,_| s.next }
  str #=> "004"

which does not mutate str.

I know what you're thinking: this isn't very efficient.

Edited to incorporate Stefan's first suggestion. Initially I implemented his second suggestion as well, but I've gone back to next and next!. I just think next reads better than succ, and they're clearly methods, so I'm not worried about them being confused with the next keyword.

Upvotes: 4

user815693
user815693

Reputation: 516

def sum_string(string, number)
    return string.scan(/^0*/)[0]+(string.to_i+number).to_s  
end
puts sum_string("00030", 5)

puts sum_string("00006", 7) 
    returns 000013 which is adding one more zero at the beginning

So, this is a slight improvement 

def sum_string(string, number)
    len = (string.scan(/^0*/)[0]+(string.to_i+number).to_s).length - string.length
    if len > 0 then
        return string.scan(/^0*/)[0][len..-1]+(string.to_i+number).to_s 
    else
        return string.scan(/^0*/)[0]+(string.to_i+number).to_s  
    end
end

Upvotes: 0

mhawke
mhawke

Reputation: 87134

Use to_i to convert str to an integer, add num to it, then convert the resulting integer to a string with to_s. Zero padding is done using rjust(). 

str = "001"  
num = 3
(str.to_i + num).to_s.rjust(3, '0')
=> "004"

Upvotes: 1

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