CODEWITHSUNDEEP
arraysrubysum
Taj
Taj

Reputation: 107

How do I get a sum of negative numbers in an array?

I want to input 2 numbers and calculate the total of the numbers in between the 2 numbers and it self. eg (1,3) 1+2+3 = 6

I have tried the code below, this works with 2 positives however this does not add up positive + negative and returns 0 everytime

def get_sum(a,b)
 if a > b || a < b 
  num_array = (a..b).to_a.sum
  puts num_array
  else 
  puts a
 end
end

get_sum(2,-3)

expected -3 instead returns 0

Upvotes: 3

Views: 1541

Answers (4)

Himanshu Goyal
Himanshu Goyal

Reputation: 11

(x..y).to_a.sum

where x is the range starting number and y is the last element. Refer to:
https://ruby-doc.org/core-2.2.0/Range.html

Upvotes: 1

iGian
iGian

Reputation: 11193

Just for fun, mixing up for Ruby 2.6:

x, y = 2, -3
[x,y].tap{ |a| a.reverse! if a[0] > a[1] }.then{ |x,y| (x..y).sum }
#=> -3

Upvotes: 0

Cary Swoveland
Cary Swoveland

Reputation: 110685

You want the sum of an algebraic series.

def get_sum(a,b)
  ((a-b).abs+1)*(a+b)/2
end

get_sum( 1,  4)  #=>  10 
get_sum( 4,  1)  #=>  10 
get_sum(-4, -1)  #=> -10 
get_sum(-1, -4)  #=> -10
get_sum(-3,  4)  #=>   4
get_sum( 4, -3)  #=>   4
get_sum(-4,  3)  #=>  -4 
get_sum( 3, -4)  #=>  -4

(a-b).abs+1 is the number of elements in the series.

Upvotes: 6

hashrocket
hashrocket

Reputation: 2222

What you can do is reverse the order of the numbers if the end value is greater than the beginning value:

a, b = b, a if a > b

According to the book "Programming Ruby", the Range object stores the two endpoints of the range and uses the .succ member to generate the intermediate values.

Upvotes: 4

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