On a number axis(One dimension), there are a bunch of points, each point have speed(to left or to right). Compute minumum time that two point meet

I have question about this question. How can I compute the minimum time for two points to meet in O(N) time.

All I can think is brutely compute point pair and get the minimum.

Can anyone give me some hints?

When using Counterspell, do you add your spell attack or any other modifiers to your roll when trying to meet the DC?

When using counterspell, do you add your spell attack or any other modifiers to your roll when trying to meet the DC?

Situation:

An enemy casts an 8th-level spell. You cast counterspell at base 3rd level, which means you have to roll to meet the DC (equal to 10 + the spell’s level). In this case, the DC is 10 + 8 = 18. When rolling for counterspell, you roll a 16. Can you add your spell attack modifier or any other modifier to the spellcasting ability check to pass the DC of 18?

What is the difference of the Join and Meet operators to the Logical AND and OR?

I’m german and I’ve encountered the words join and meet particularely in the context of lattices alot.

I can’t figure out the german equivalents/translations to those words, they seem like the logical conjunction and disjunction AND and OR to me?

Am I mixing things up here a bit? What’s the deifference between them and could someone maybe from germany she some light on the topic?