FA-72718 / Check-digit algorithms / Member archive

Container letter values do not skip multiples of eleven · case 03

Container numbers with owner letters B or later get the wrong check digit.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Shipping container identification check digit: three uppercase owner letters, category U, J or Z, six serial digits and a check digit (else "malformed"). Letter values start at A=10 and skip every multiple of 11 (so B=12, L=23, V=34, Z=38). Position i (0-based) has weight 2^i; the check digit is (sum mod 11) mod 10. Return [check, match].

Why this case matters

Terminal gate systems validate container numbers read by OCR cameras before booking moves.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression ["CYVU1050697"]	`[5, false]`	`[7, true]`	Failed

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