Rotating Top-Scored Title Service (Upsert + GetTop with No-Immediate-Repeat)
Question Details
Problem: Top Title Selection Service with “No Immediate Repeat” Rotation
Implement a service that selects one movie/show title to display on a user’s homepage billboard. The system maintains a rel
Full Details
Problem: Top Title Selection Service with “No Immediate Repeat” Rotation
Implement a service that selects one movie/show title to display on a user’s homepage billboard. The system maintains a relevance score score for each title_id.
You must support two APIs:
upsertTitleScore(title_id: str, score: float): Insert a new title or update an existing title’s score.getTopTitle() -> str:
Return the title_id that should be displayed now.
Requirements
1.
Higher score has priority: Among available titles, the service should prefer returning the title with the highest score.
2.
Avoid immediate repeats: If there exists any other selectable title, getTopTitle() should not return the same title_id in two consecutive calls.
3.
Titles can reappear: After a title is returned, it may be returned again in later calls (subject to rules 1 and 2).
4.
Single-title case: If the system contains only one title, it may be returned repeatedly.
5.
Repeated upserts: upsertTitleScore may be called multiple times for the same title_id; the score must be updated correctly.
Expectations
- Explain your data structure choices and implement both APIs.
- Handle how score updates affect subsequent
getTopTitle()results. - Discuss time/space complexity goals for
upsertandgetTopTitle.
Examples (illustrative)
- Start:
upsert(A, 10),upsert(B, 9) - First
getTopTitle()
returns A
- Second call should return B (no immediate repeat of A)
- Third call may return A again
- Start: upsert(A, 10)
- Repeated getTopTitle() calls can keep returning A
Test Cases (stdin/stdout style)
Use
GETforgetTopTitle()andUPSERT id scoreforupsertTitleScore.
1) Two-title rotation
input
UPSERT A 10
UPSERT B 9
GET
GET
GET
GET
-
output (one valid output)
A
B
A
B
2) Single title repeats
input
UPSERT A 10
GET
GET
GET
-
output
A
A
A
3) Upsert update changes ordering
input
UPSERT A 10
UPSERT B 9
GET
UPSERT B 100
GET
GET
-
output (must prioritize B after the update and avoid immediate repeats)
A
B
A
4) Three titles; avoid immediate repeats and prefer the highest
input
UPSERT A 10
UPSERT B 9
UPSERT C 8
GET
GET
GET
GET
GET
-
output (one valid output)
A
B
A
B
A
5) Ties (you may define a deterministic tie-break rule)
input
UPSERT A 10
UPSERT B 10
GET
GET
GET
-
output (example)
A
B
A
Sample Input
UPSERT A 10
UPSERT B 9
GET
GET
GET
GET
Sample Output
A
B
A
B
Test Cases
Case 1
Input:
UPSERT A 10
UPSERT B 9
GET
GET
GET
GET
Output:
A
B
A
B
Case 2
Input:
UPSERT A 10
GET
GET
GET
Output:
A
A
A
Case 3
Input:
UPSERT A 10
UPSERT B 9
GET
UPSERT B 100
GET
GET
Output:
A
B
A
Case 4
Input:
UPSERT A 10
UPSERT B 9
UPSERT C 8
GET
GET
GET
GET
GET
Output:
A
B
A
B
A
Case 5
Input:
UPSERT A 10
UPSERT B 10
GET
GET
GET
Output:
A
B
A
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