FA-94694 / Exam timetabling constraints / Member archive

Conflict matrix stores a flag instead of a student count · case 04

Heavily shared exam pairs weigh the same as pairs with one shared student.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

enrol rows [student, exam] (may repeat). For every unordered pair of distinct exams (a < b) count the students enrolled in both. Return [a, b, count] rows sorted, omitting zero counts.

Why this case matters

The conflict matrix is the input to every exam timetabling algorithm; count errors silently change weights.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: pair count increment 1	`[["BIO130", "ECON150", 1], ["BIO130", "HIST140", 1], ["BIO130", "MATH101", 1], ["ECON150", "HIST140", 1], ["ECON150", "MATH101", 1], ["HIST140", "MATH101", 1]]`	`[["BIO130", "ECON150", 1], ["BIO130", "HIST140", 3], ["BIO130", "MATH101", 1], ["ECON150", "HIST140", 1], ["ECON150", "MATH101", 1], ["HIST140", "MATH101", 1]]`	Failed

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