yellow_flash

they should be the same
This is the main problem which I am facing - I feel that units in ring theory are somehow correlated to 1 and -1 (in $\Bbb Z$) ; there are also statements like - factorization in UFD are unique upto units

I'm having some difficulty wrapping my head around the concept of units in ring theory. One such troubling instance is - In a ring $R$, if $p$ is a prime such that $p = am$, where $p, a, m \in R$ and $a$ is a unit, then $(p) = (m)$ (the ideals generated are equal). How do I go about reasoning this ?
Thanks in advance!

I was reading about [in-place algorithms](https://www.wikiwand.com/en/In-place_algorithm), and there is this one statement which I am not able to understand ~
```
However, this form is very limited as simply having an index to a length n array requires O(log n) bits.
```
I was hoping it would be very helpful if someone can help me figure out the meaning of this statement.
Thanks.