How many times can a Lvl 17 Astral Self Monk attack, including bonus action

I believed this was straight forward, but I had a discussion with one of my players who didn’t see it the same way as I did.

According to the subclass features, at 3rd level:

[…] immediately after you use the Attack action with your astral arms on your turn, you can make one extra attack with your astral arms as a bonus action. The number of extra attacks increases when you reach certain levels in this class, increasing to two at 11th level and three at 17th level.

Pretty straight forward: at level 3, you can make a total of two attacks (1A and 1BA), at level 11 three attacks (1A and 2BA) and at level 17 four attacks (1A and 3BA)

Then at level 5 as every martial class you get Extra Attack:

Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.

Also, at level 17 you get the “Complete Astral Self” feature, which provides the following benefit among other:

Astral Barrage. Whenever you use the Extra Attack feature to attack twice, you can instead attack three times using your astral arms.

The difference of opinion lies on whether the Extra Attack feature, means you are taking the Attack action. As such my player suggests that the astral self monk scales as follows:

  • at 3rd level can make 2 attacks (1A and 1BA)
  • at 5th level can make 4 attacks (1A + 1BA + 1 extra attack + 1 astral self attacks (1 per attack action taken) as BA)
  • at 11th level can make 8 attacks (1A + 1 extra attack + 4 astral self attacks (2 per attack action taken) as BA)
  • at 17th level can make 12 attacks (1A + 2 extra attack + 9 astral self attacks (3 per attack action taken) as BA)

First of all, that seems absurd, even if it satisfies my Jojo fantasy. The way I interpret is:

  • at level 17th he could make 6 attacks (1A + 2 Extra attack + 3 astral self attacks as bonus action).

All of the instances above take into account the BA the monk would have needed to summon the astral self.

What are your thoughts? I feel that typing this out, solidified that the answer should be 6 attacks, but I would like to hear other people’s opinions on the matter.

Why does MergeSort have O(n) space complexity if it splits the array log(n) times?

I know this is a common algorithm with plenty of analysis, but when I searched for an answer the only one I found was “Merge Sorting has O(n) auxiliary space because it copies the array into L and R”.

I don’t understand this because as it is called recursively, before performing any operations, the entire array is still split log(n) times. When following the binary tree diagram representing the recursion, we see (if n=16) it splits into 2×8, 4×4, 8×2, 16×1.

Since all of these splits occur prior to any merging, why is the auxiliary space O(n) and not O(nlog(n))?

How many times in this pseudocode is the function F called?

For this question, I thought function F called twice but it called three times. Are those three functions were called? F(N), F(K) and f(N-1)?

How many times in this pseudocode is the function F called?

Main     Declare K as Integer     K = 3     Set Result = F(K)     Write Result End Program  Function F(N) as Integer         If N == 1 Then Set F = 1     Else         Set F = N * F(N - 1)         Set N = N - 1     End If End Function 

Can a fighter use Indomitable multiple times on the same save?

Our fighter, Fred, is a high level fighter with multiple uses of the Indomitable feature:

Beginning at 9th level, you can reroll a saving throw that you fail. If you do so, you must use the new roll, and you can’t use this feature again until you finish a long rest.

You can use this feature twice between long rests starting at 13th level and three times between long rests starting at 17th level.

Let’s suppose Fred is targeted by the Hold Person spell. Fred rolls a 5 and fails the save. Fred uses one use of his Indomitable feature, to reroll the save, but still fails. Can Fred expend a second use of his Indomitable feature to reroll the save again?

Also, does this answer hold for the Champion and Warlord NPCs?

Indomitable (2/Day). The champion rerolls a failed saving throw.

Indomitable (3/Day). The warlord can reroll a saving throw it fails. It must use the new roll.

When a spell asks for targets, can I choose the same target multiple times?

When a spell has multiple targets, can I choose the same target multiple times?

Is there any general rule I can refer to?

An example of ambiguity is the spell Steel Wind Strike:

You flourish the weapon used in the casting and then vanish to strike like the wind. Choose up to five creatures you can see within range. Make a melee spell attack against each target. On a hit, a target takes 6d10 force damage. You can then teleport to an unoccupied space you can see within 5 feet of one of the targets you hit or missed.

Nowhere does it say you have to choose up to five different creatures, although Crawford has disallowed targeting the same creature multiple times on Sage Advice EU. However, this answer does not give light on a general rule.

Similarly, for Acid Splash:

You hurl a bubble of acid. Choose one creature within range, or choose two creatures within range that are within 5 feet of each other. A target must succeed on a Dexterity saving throw or take 1d6 acid damage.

The intended answer is clearly no. But how can I know that? Is there a general rule?

What happens when multiple polymorph effects on a single target end at different times?

I was inspired to ask this question from a post about using a tankard to fight people.

Here’s the scenario: A tiny object, in this case a Tankard, has been turned into a tiny construct thanks to the Tiny Servant spell, and will remain as such for 8 hours (the spells duration). It is subsequently targeted by a True Polymorph turning it into a different creature, lets say a bat. True Polymorph states that if the caster maintains concentration for the full duration (1 hour), the effect becomes permanent. If such a circumstance occurred

What happens to the bat when Tiny Servant ends?

If it remains a bat, and is subsequently brought to 0 HP (not difficult, considering it only has 1 HP) does it return to being a tankard then, or is it just a dead bat?

What’s a quick test to see if an $n \times n$ matrix is diagonal and/or proporitional to the identity matrix?

As the title indicates, I want to test whether an $ n \times n$ matrix (numeric, symbolic,..) is diagonal and/or proportional to the $ n \times n$ identity matrix. I, of course, can test whether the $ n^2-n$ individual off-diagonal entries are zero–but that’s, it would seem, is inefficient.

Can the cantrips gained from the Dragonmark feat be cast multiple times?

The Dragonmark Feat from Unearthed Arcana: Eberron says:

You gain the ability to innately cast spells and cantrips, as summarized in the Dragonmark Benefits table, using the spellcasting ability listed under the Ability column. You cast each spell at its lowest level. Once you cast a given spell this way, you must finish a long rest before you can cast it innately again. You must still expend any material components.

Every dragonmark gives the character access to a first, second and third level spell, as well as a cantrip. The second and third level spells can only be cast if the character is of high enough level (, 5th and 9th, respectively).

Usually you can cast the cantrips you know infinitely often. But the way this feat is worded seems to imply, that the cantrips gained from dragonmarks are treated exactly like the other spells, which means their use is limited to once per day. I’m am not sure if I interpret this correctly, if this is intended this way, or just worded weirdly.