Example 1 · empty
- Arguments
- workers
1
queueLimit0
events[]
- Expected return
Empty list
Test data
- Input
{"workers":1,"queueLimit":0,"events":[]}- Expected output
[]
Bounded worker scheduling
Bounded worker scheduling
MediumYour task
- A worker pool has a fixed number of workers and a FIFO waiting room.
- Apply a sequence of events and report a snapshot after every event.
- This is a deterministic exercise in concurrency reasoning: do not create threads, goroutines, timers or background work.
Required API
- ScheduleWorkers
func ScheduleWorkers(workers, queueLimit int, events []Event) []Snapshot - Event.Kind
Kind string - Event.Job
Job string - Event.Token
Token int - Run.Job
Job string - Run.Token
Token int - Snapshot.Accepted
Accepted bool - Snapshot.Active
Active []Run - Snapshot.Waiting
Waiting []string
Behavior
- A submit event is accepted only when its job ID is neither running nor waiting, and a worker or waiting-room slot is available.
- Start immediately if a worker is free; otherwise append the job to the waiting room.
- Rejected submits change nothing.
- Every start receives the next global dispatch token, beginning at 1.
- Allocate tokens only when a job actually starts.
- A complete event is accepted only for a running job with the matching dispatch token.
- A cancel event is accepted only for a running or waiting job.
- An accepted completion or cancellation removes that job.
- Whenever a worker becomes free, immediately start the oldest waiting job with a fresh token.
- Cancellation here is an authoritative simulated event that releases the worker immediately; a real runner may require separate cleanup confirmation.
- A released job ID may be submitted again, so an old completion token must never finish its newer run.
- Return one Snapshot per event: Accepted indicates whether the event changed state; Active lists running jobs in dispatch order, and Waiting lists queued IDs in FIFO order.
- Previously returned snapshots must remain unchanged when later events run.
- Empty lists are represented as [].
- Do not mutate input events, and keep separate calls independent.
Constraints
- Input is valid: workers is 1–3; queueLimit is 0–3; there are 0–16 events.
- Each event has kind submit, complete or cancel, an ASCII ID matching [A-Za-z0-9_-]{1,8}, and a token from 0–1,000,000.
- Submit/cancel tokens are always 0; only complete uses the supplied token.
- Queue capacity counts waiting jobs only, excluding running jobs.
- There is no automatic completion, timeout or retry.
- Use only the standard library.
Notes and example notation
Examples encode events as [kind, job, token], active runs as {job, token}, and each snapshot as {accepted, active, waiting}.
Examples
The runner calls your functions directly; you do not need to parse JSON.
Example 2 · capacity and fifo
- Arguments
- workers
2
queueLimit1
events[ [ "submit", "b", 0 ], [ "submit", "A", 0 ], [ "submit", "t", 0 ], [ "submit", "x", 0 ], [ "complete", "b", 1 ] ] - Expected return
[ { "accepted": true, "active": [ { "job": "b", "token": 1 } ], "waiting": [] }, { "accepted": true, "active": [ { "job": "b", "token": 1 }, { "job": "A", "token": 2 } ], "waiting": [] }, { "accepted": true, "active": [ { "job": "b", "token": 1 }, { "job": "A", "token": 2 } ], "waiting": [ "t" ] }, { "accepted": false, "active": [ { "job": "b", "token": 1 }, { "job": "A", "token": 2 } ], "waiting": [ "t" ] }, { "accepted": true, "active": [ { "job": "A", "token": 2 }, { "job": "t", "token": 3 } ], "waiting": [] } ]
Test data
- Input
{"workers":2,"queueLimit":1,"events":[["submit","b",0],["submit","A",0],["submit","t",0],["submit","x",0],["complete","b",1]]}- Expected output
[{"accepted":true,"active":[{"job":"b","token":1}],"waiting":[]},{"accepted":true,"active":[{"job":"b","token":1},{"job":"A","token":2}],"waiting":[]},{"accepted":true,"active":[{"job":"b","token":1},{"job":"A","token":2}],"waiting":["t"]},{"accepted":false,"active":[{"job":"b","token":1},{"job":"A","token":2}],"waiting":["t"]},{"accepted":true,"active":[{"job":"A","token":2},{"job":"t","token":3}],"waiting":[]}]
Example 3 · cancel promotes
- Arguments
- workers
1
queueLimit2
events[ [ "submit", "a", 0 ], [ "submit", "b", 0 ], [ "submit", "c", 0 ], [ "cancel", "b", 0 ], [ "cancel", "a", 0 ], [ "complete", "a", 1 ] ] - Expected return
[ { "accepted": true, "active": [ { "job": "a", "token": 1 } ], "waiting": [] }, { "accepted": true, "active": [ { "job": "a", "token": 1 } ], "waiting": [ "b" ] }, { "accepted": true, "active": [ { "job": "a", "token": 1 } ], "waiting": [ "b", "c" ] }, { "accepted": true, "active": [ { "job": "a", "token": 1 } ], "waiting": [ "c" ] }, { "accepted": true, "active": [ { "job": "c", "token": 2 } ], "waiting": [] }, { "accepted": false, "active": [ { "job": "c", "token": 2 } ], "waiting": [] } ]
Test data
- Input
{"workers":1,"queueLimit":2,"events":[["submit","a",0],["submit","b",0],["submit","c",0],["cancel","b",0],["cancel","a",0],["complete","a",1]]}- Expected output
[{"accepted":true,"active":[{"job":"a","token":1}],"waiting":[]},{"accepted":true,"active":[{"job":"a","token":1}],"waiting":["b"]},{"accepted":true,"active":[{"job":"a","token":1}],"waiting":["b","c"]},{"accepted":true,"active":[{"job":"a","token":1}],"waiting":["c"]},{"accepted":true,"active":[{"job":"c","token":2}],"waiting":[]},{"accepted":false,"active":[{"job":"c","token":2}],"waiting":[]}]
Example 4 · stale completion
- Arguments
- workers
1
queueLimit0
events[ [ "submit", "a", 0 ], [ "cancel", "a", 0 ], [ "submit", "a", 0 ], [ "complete", "a", 1 ], [ "complete", "a", 2 ] ] - Expected return
[ { "accepted": true, "active": [ { "job": "a", "token": 1 } ], "waiting": [] }, { "accepted": true, "active": [], "waiting": [] }, { "accepted": true, "active": [ { "job": "a", "token": 2 } ], "waiting": [] }, { "accepted": false, "active": [ { "job": "a", "token": 2 } ], "waiting": [] }, { "accepted": true, "active": [], "waiting": [] } ]
Test data
- Input
{"workers":1,"queueLimit":0,"events":[["submit","a",0],["cancel","a",0],["submit","a",0],["complete","a",1],["complete","a",2]]}- Expected output
[{"accepted":true,"active":[{"job":"a","token":1}],"waiting":[]},{"accepted":true,"active":[],"waiting":[]},{"accepted":true,"active":[{"job":"a","token":2}],"waiting":[]},{"accepted":false,"active":[{"job":"a","token":2}],"waiting":[]},{"accepted":true,"active":[],"waiting":[]}]
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