fix(be): fix contest leaderboard ranking malfunction

[zero1177]

Description

Contest 리더보드 순위 표시가 잘못된 문제 수정

contest 7 기준으로 테스트

contestProblem 문제는 problemId 5,6,7,8 총 4개이고 (점수 각각 50, 60, 70, 80)

user02~user08 까지 7명의 user가 참여했다는 가정

• solvedProblemCount가 동일할 경우, penalty가 적은 user가 상위 rank임을 테스트 완료
• solvedProblemCount, penalty까지 모두 동일할 경우 동점 처리 확인

ex) 공동 4등 2명이면, 다음은 6등

const testData = [
{
// user02 (2등) 3솔
scores: [50, 60, 70, 0],
penalties: [30, 30, 40, 0]
},
{
// user03 (1등) 4솔
scores: [50, 60, 70, 80],
penalties: [15, 100, 55, 200]
},
{
// user04 (3등) 3솔
scores: [0, 60, 70, 80],
penalties: [0, 150, 20, 300]
},
{
// user05 (6등) 2솔
scores: [0, 0, 70, 80],
penalties: [0, 0, 150, 100]
},
{
//user06 (7등) 1솔
scores: [0, 0, 70, 0],
penalties: [0, 0, 150, 0]
},
{
//user07 (공동 4등) 2솔
scores: [50, 60, 0, 0], //110
penalties: [20, 35, 0, 0] //55
},
{
//user08 (공동 4등) 2솔
scores: [0, 60, 70, 0], //130
penalties: [0, 35, 20, 0] //55
}
]

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• Read the Contributing Guidelines
• Read the Contributing Guidelines and follow the Commit Convention
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

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[hjkim24]

/gemini review

[gemini-code-assist]

Code Review

This pull request refactors the contest leaderboard calculation logic in ContestService, introducing custom sorting and ranking based on solved problems and penalties, and adds new seeding data for contestId7 to test these changes. The review highlights a performance regression in ContestService due to sequential database queries that should be parallelized using Promise.all. Additionally, the new ranking logic in ContestService does not correctly handle ties, and a related comment is misleading. In prisma/seed.ts, the newly created contest7Records are not included in the function's return value, and there's a typo in a comment describing the number of solved problems for a test user.