Every a Before Every b

Easy

Two kinds of visitors stand in a queue: those with a booking (a) and walk-ins (b). The queue is written as a string queue of the letters a and b. The rule says everyone with a booking must stand ahead of every walk-in. Return True if no a comes after any b, and False otherwise. If one of the letters is missing entirely, the rule holds.

Example 1

queue="aaab" → True

All three as come before the only b.

Example 2

queue="abba" → False

The last a comes after two bs.

Example 3

queue="aa" → True

There are no bs, so no a comes after a b.

Constraints

1 ≤ len(queue) ≤ 100
queue consists only of the letters a and b

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Topics

String

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Input

queue="aaab"

Expected

True

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