No, because the two conditions do not encompass every possibility.
If the Swashbuckler (S) has interposed himself between an Ally (A) and an Opponent (O). Each occupies a single five by five square.
Such as:
ASO
In this scenario, an ally is within 5 feet from the swashbuckler, but there isn't an ally within 5 feet of the opponent. Lacking an additional effect that will provide advantage to the Swashbuckler, Sneak Attack won't be available.
Similarly, if the Swashbuckler (S) is facing two Opponents (O and X), there are several configurations in which Sneak Attack isn't available.
To summarize, the following conditions will prohibit you from using Sneak Attack, assuming there isn't an external effect providing Advantage.
- Swashbuckler is within 5 feet of more than one hostile creature or character.
- Swashbuckler is attacking the target at melee range and a friendly character or creature is within 5 feet of him but isn't within 5 feet of the target.
Per a twitter post by Jeremy Crawford, Rules as Intended want the Swashbuckler to be within 5 feet of the target. In effect, Rackish Audacity should be written with "except" instead of "other."
No, It does not.
FLANKING
When making a melee attack, you get a +2 flanking bonus if your opponent is threatened by a character or creature friendly to you on
the opponent’s opposite border or opposite corner.
When in doubt about whether two friendly characters flank an opponent
in the middle, trace an imaginary line between the two friendly
characters’ centers. If the line passes through opposite borders of
the opponent’s space (including corners of those borders), then the
opponent is flanked.
The rogue is not in a flanking position. So does not get the bonus.
Sneak Attack
If a rogue can catch an opponent when he is unable to defend himself
effectively from her attack, she can strike a vital spot for extra
damage.
The rogue’s attack deals extra damage any time her target would be
denied a Dexterity bonus to AC (whether the target actually has a
Dexterity bonus or not), or when the rogue flanks her target.
Key words here, Her attack. The rogue does not have a flanking position bonus so does not get to sneak attack.
- The warrior get flanking bonus to hit. The rogue does not.
- No. The rogue does not get sneak attack.
Best Answer
Yes, despite the name, flanking lets you Sneak Attack without actually being sneaky.
When flanking someone with the help of the an ally, your rogue has no need to be stealthy in order to benefit from the Sneak Attack ability. The ability's rules just let you do it.
The idea is that, when someone is flanked, they can't defend as effectively — either way they turn, they have to put a side or a back to an enemy. The Sneak Attack ability, despite the name, really means the ability to exploit someone's weakened defenses to attack them in a vulnerable spot (PHB, p. 50, emphasis mine):
Sneak Attack does also let you hurt people more when you attack them stealthily — but stealth gives that opportunity for the same reason flanking does: because they're unable to properly defend against the attack. That's what it always comes back to: do they have vulnerable spots they're not defending properly. Flanking someone creates that opportunity.