Sum of positive (8kyu) [Ruby]

Chek kata on Codewars

Description:

You get an array of numbers, return the sum of all of the positives ones.

Example [1,-4,7,12] => 1 + 7 + 12 = 20

Note: if there is nothing to sum, the sum is default to 0.

Solution 1.1

Let's use reduce method to solve this task. It executes a reducer function (that you provide) on each element of the array, resulting in single output value. It is almost a textbook example for reducer.

def positive_sum(arr)
  arr.reduce(0) {|acc, cur| acc + (cur > 0 ? cur : 0)}
end

Solution 1.2

def positive_sum(arr)
  arr.select{|num| num > 0}.reduce(0, :+)
end

Solution 2.1

Also we can use sum from Enumerables.

def positive_sum(arr)
  arr.select{|num| num > 0}.sum
end

Solution 2.2

def positive_sum(arr)
  arr.select(&:positive?).sum
end

Solution 3.1

Another approach will be to loop over the array and sum all positive numbers.

def positive_sum(arr)
    sum = 0
    arr.each do |num|
        if num > 0
            sum += num
        end
    end
    sum
end

Solution 3.2

def positive_sum(arr)
    sum = 0
    arr.each do |num|
        if num.positive?
            sum += num
        end
    end
    sum
end