merge_sort.rb

def merge(left, right)
    result = []
    while left.size > 0 and right.size > 0
        if left[0] <= right[0]
            result << left[0]
            left = left[1..-1]
        else
            result << right[0]
            right = right[1..-1]    
        end
    end
    if left.size > 0
        result.concat left
    end
    if right.size > 0
        result.concat right
    end
    return result
end

def merge_sort(arr)
    left, right, result = []    
    
    if arr.size <= 1
        return arr
    else
        middle = arr.size / 2
        left = arr[0..middle - 1]
        right = arr[middle..-1]
        left = merge_sort(left)
        right = merge_sort(right)
        if left.last <= right[0]
            left.concat right
            return left
        end
        result = merge(left, right)
        return result
    end
end
arr = [1,4,54,2545,23,524,5,2435,432,543,25,2435,2]
puts merge_sort(arr)