Add solutions for fibonacci seq (iter and rec) and mergesort
user
```ruby
def fibs(num)
    curr = 0
    next_num = 1
    temp = 0
    while (num -= 1) > 0 do
        temp = curr + next_num
        curr = next_num
        next_num = temp
    end
    return next_num
end

def fibs_rec(num)
    if num < 2 then
        return num
    else
        return fibs_rec(num - 1) + fibs_rec(num - 2)
    end
end

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 = [3, 1, 5, 2]
puts arr
puts merge_sort(arr)
```
assistant