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FA-83891 / Sports scoring and tiebreakers / Open access

Best-of-five match decided after the wrong number of sets · case 01

A best-of-five match is declared over while a player has only two sets.

Verified by executionVariant 1 · 10 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The number of sets needed is computed as best_of // 2.

VERIFIED REPAIR

Require best_of // 2 + 1 sets.

Unsuccessful approach: Using best_of - 1 is right for best-of-three but requires four sets in best-of-five.

Case contract

games is a string of game winners (A/B); best_of is 3 or 5. A set is won by the first player to 6 games with a lead of two, or at 7 games (7-5, or 7-6 after the tiebreak game played at 6-6). The match ends when a player has won best_of // 2 + 1 sets; later games are ignored. Return [set scores as "a-b" strings in A-B order, match winner or None]; an unfinished set with at least one game is appended as its current score.

Why this case matters

Tournament live-results feeds reconstruct set scores from game-level events.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(games, best_of):
    sets = []
    a = b = 0
    won = {'A': 0, 'B': 0}
    need = best_of // 2
    for g in games:
        if g == 'A':
            a += 1
        else:
            b += 1
        if (max(a, b) >= 6 and abs(a - b) >= 2) or max(a, b) == 7:
            w = 'A' if a > b else 'B'
            won[w] += 1
            sets.append('%d-%d' % (a, b))
            a = b = 0
            if won[w] == need:
                return [sets, w]
    if a or b:
        sets.append('%d-%d' % (a, b))
    return [sets, None]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
def run(args):
    try:
        return solve(*args)
    except Exception as exc:
        return 'raised ' + type(exc).__name__
cases = [[('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('BAAABBAAABBA', 3), [['6-3', '1-2'], None]),
  ('regression: sets needed', ('AAAAAABBBABAAAAABAABBAAAABBB', 5), [['6-0', '6-4', '6-3'], 'A']),
  ('variant scenario 1', ('AABBBABBA', 3), [['4-5'], None]),
  ('variant scenario 2', ('AAABAAAABBBABBB', 5), [['6-1', '2-6'], None])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('AAAAABAABBBAAAAAAABBBAAABBBAA', 3), [['6-1', '6-3'], 'A']),
  ('regression: sets needed', ('BBAABAAAAABBAAABBAAAAAAAA', 5), [['6-3', '6-4', '6-0'], 'A']),
  ('variant scenario 1', ('ABBAABAABBAABABB', 3), [['7-5', '1-3'], None]),
  ('variant scenario 2', ('AABAAAAABAABBABAABABBAAAABA', 3), [['6-1', '6-4'], 'A'])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('BBABBBBBBABAABBBBAAABBBABBABBAB', 5), [['1-6', '3-6', '4-6'], 'B']),
  ('variant scenario 1', ('AAABAA', 5), [['5-1'], None]),
  ('variant scenario 2', ('AABAABBBAABAAAABBAAABAAB', 5), [['6-4', '6-3', '3-2'], None])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('ABBABBAABBABABA', 3), [['4-6', '3-2'], None]),
  ('regression: sets needed',
   ('AAAAAAAAABABBBAAABAABAAABABAAAABABBB', 5),
   [['6-0', '6-4', '6-2'], 'A']),
  ('variant scenario 1', ('BABAA', 3), [['3-2'], None]),
  ('variant scenario 2',
   ('BAABABBBAAAAABBBAABBABBABAAABBAAAABBBABAABAABABBA', 3),
   [['7-5', '4-6', '6-4'], 'A'])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('BABAAABBAAAABAAABAABBABBBBAAA', 3), [['6-4', '6-2'], 'A']),
  ('regression: sets needed',
   ('AAAAAAAABAAAAAAABAAAABAABBAAAAAABAABBAAABA', 5),
   [['6-0', '6-1', '6-1'], 'A']),
  ('variant scenario 1',
   ('BBBABBBAAABAAAAAAAAABABAAABAAAAAABABA', 3),
   [['1-6', '6-1', '6-0'], 'A']),
  ('variant scenario 2', ('BBAAAAAABABBABBABAAAAAAAAABAABBA', 3), [['6-2', '3-6', '6-0'], 'A'])]]
for label, args, expected in cases[N - 1]:
    check(label, run(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
control bagel set[['6-0'], 'A'][['6-0'], None]Failed
boundary seven-five[['7-5'], 'A'][['7-5'], None]Failed
boundary tiebreak set[['6-7'], 'B'][['6-7'], None]Failed
control straight sets[['6-0'], 'A'][['6-0', '6-0'], 'A']Failed
control in-progress set[['6-0'], 'A'][['6-0', '0-1'], None]Failed
control empty[[], None][[], None]Passed
regression: sets needed[['6-3'], 'A'][['6-3', '1-2'], None]Failed
regression: sets needed[['6-0', '6-4'], 'A'][['6-0', '6-4', '6-3'], 'A']Failed
variant scenario 1[['4-5'], None][['4-5'], None]Passed
variant scenario 2[['6-1', '2-6'], None][['6-1', '2-6'], None]Passed

SHA-256 / 9a2c29352e2f8e63c7a16d7d6690298c21c429d5cd8e6735a7a204939b55577f

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(games, best_of):
    sets = []
    a = b = 0
    won = {'A': 0, 'B': 0}
    need = best_of - 1
    for g in games:
        if g == 'A':
            a += 1
        else:
            b += 1
        if (max(a, b) >= 6 and abs(a - b) >= 2) or max(a, b) == 7:
            w = 'A' if a > b else 'B'
            won[w] += 1
            sets.append('%d-%d' % (a, b))
            a = b = 0
            if won[w] == need:
                return [sets, w]
    if a or b:
        sets.append('%d-%d' % (a, b))
    return [sets, None]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
def run(args):
    try:
        return solve(*args)
    except Exception as exc:
        return 'raised ' + type(exc).__name__
cases = [[('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('BAAABBAAABBA', 3), [['6-3', '1-2'], None]),
  ('regression: sets needed', ('AAAAAABBBABAAAAABAABBAAAABBB', 5), [['6-0', '6-4', '6-3'], 'A']),
  ('variant scenario 1', ('AABBBABBA', 3), [['4-5'], None]),
  ('variant scenario 2', ('AAABAAAABBBABBB', 5), [['6-1', '2-6'], None])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('AAAAABAABBBAAAAAAABBBAAABBBAA', 3), [['6-1', '6-3'], 'A']),
  ('regression: sets needed', ('BBAABAAAAABBAAABBAAAAAAAA', 5), [['6-3', '6-4', '6-0'], 'A']),
  ('variant scenario 1', ('ABBAABAABBAABABB', 3), [['7-5', '1-3'], None]),
  ('variant scenario 2', ('AABAAAAABAABBABAABABBAAAABA', 3), [['6-1', '6-4'], 'A'])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('BBABBBBBBABAABBBBAAABBBABBABBAB', 5), [['1-6', '3-6', '4-6'], 'B']),
  ('variant scenario 1', ('AAABAA', 5), [['5-1'], None]),
  ('variant scenario 2', ('AABAABBBAABAAAABBAAABAAB', 5), [['6-4', '6-3', '3-2'], None])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('ABBABBAABBABABA', 3), [['4-6', '3-2'], None]),
  ('regression: sets needed',
   ('AAAAAAAAABABBBAAABAABAAABABAAAABABBB', 5),
   [['6-0', '6-4', '6-2'], 'A']),
  ('variant scenario 1', ('BABAA', 3), [['3-2'], None]),
  ('variant scenario 2',
   ('BAABABBBAAAAABBBAABBABBABAAABBAAAABBBABAABAABABBA', 3),
   [['7-5', '4-6', '6-4'], 'A'])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('BABAAABBAAAABAAABAABBABBBBAAA', 3), [['6-4', '6-2'], 'A']),
  ('regression: sets needed',
   ('AAAAAAAABAAAAAAABAAAABAABBAAAAAABAABBAAABA', 5),
   [['6-0', '6-1', '6-1'], 'A']),
  ('variant scenario 1',
   ('BBBABBBAAABAAAAAAAAABABAAABAAAAAABABA', 3),
   [['1-6', '6-1', '6-0'], 'A']),
  ('variant scenario 2', ('BBAAAAAABABBABBABAAAAAAAAABAABBA', 3), [['6-2', '3-6', '6-0'], 'A'])]]
for label, args, expected in cases[N - 1]:
    check(label, run(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
control bagel set[['6-0'], None][['6-0'], None]Passed
boundary seven-five[['7-5'], None][['7-5'], None]Passed
boundary tiebreak set[['6-7'], None][['6-7'], None]Passed
control straight sets[['6-0', '6-0'], 'A'][['6-0', '6-0'], 'A']Passed
control in-progress set[['6-0', '0-1'], None][['6-0', '0-1'], None]Passed
control empty[[], None][[], None]Passed
regression: sets needed[['6-3', '1-2'], None][['6-3', '1-2'], None]Passed
regression: sets needed[['6-0', '6-4', '6-3', '0-3'], None][['6-0', '6-4', '6-3'], 'A']Failed
variant scenario 1[['4-5'], None][['4-5'], None]Passed
variant scenario 2[['6-1', '2-6'], None][['6-1', '2-6'], None]Passed

SHA-256 / d1f939836417cc7645e8ad999a8fb8eab1addaec82cdd2211b80b249403807ff

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(games, best_of):
    sets = []
    a = b = 0
    won = {'A': 0, 'B': 0}
    need = best_of // 2 + 1
    for g in games:
        if g == 'A':
            a += 1
        else:
            b += 1
        if (max(a, b) >= 6 and abs(a - b) >= 2) or max(a, b) == 7:
            w = 'A' if a > b else 'B'
            won[w] += 1
            sets.append('%d-%d' % (a, b))
            a = b = 0
            if won[w] == need:
                return [sets, w]
    if a or b:
        sets.append('%d-%d' % (a, b))
    return [sets, None]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
def run(args):
    try:
        return solve(*args)
    except Exception as exc:
        return 'raised ' + type(exc).__name__
cases = [[('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('BAAABBAAABBA', 3), [['6-3', '1-2'], None]),
  ('regression: sets needed', ('AAAAAABBBABAAAAABAABBAAAABBB', 5), [['6-0', '6-4', '6-3'], 'A']),
  ('variant scenario 1', ('AABBBABBA', 3), [['4-5'], None]),
  ('variant scenario 2', ('AAABAAAABBBABBB', 5), [['6-1', '2-6'], None])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('AAAAABAABBBAAAAAAABBBAAABBBAA', 3), [['6-1', '6-3'], 'A']),
  ('regression: sets needed', ('BBAABAAAAABBAAABBAAAAAAAA', 5), [['6-3', '6-4', '6-0'], 'A']),
  ('variant scenario 1', ('ABBAABAABBAABABB', 3), [['7-5', '1-3'], None]),
  ('variant scenario 2', ('AABAAAAABAABBABAABABBAAAABA', 3), [['6-1', '6-4'], 'A'])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('BBABBBBBBABAABBBBAAABBBABBABBAB', 5), [['1-6', '3-6', '4-6'], 'B']),
  ('variant scenario 1', ('AAABAA', 5), [['5-1'], None]),
  ('variant scenario 2', ('AABAABBBAABAAAABBAAABAAB', 5), [['6-4', '6-3', '3-2'], None])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('ABBABBAABBABABA', 3), [['4-6', '3-2'], None]),
  ('regression: sets needed',
   ('AAAAAAAAABABBBAAABAABAAABABAAAABABBB', 5),
   [['6-0', '6-4', '6-2'], 'A']),
  ('variant scenario 1', ('BABAA', 3), [['3-2'], None]),
  ('variant scenario 2',
   ('BAABABBBAAAAABBBAABBABBABAAABBAAAABBBABAABAABABBA', 3),
   [['7-5', '4-6', '6-4'], 'A'])],
 [('control bagel set', ('AAAAAA', 3), [['6-0'], None]),
  ('boundary seven-five', ('AAAAABBBBBAA', 3), [['7-5'], None]),
  ('boundary tiebreak set', ('AAAAABBBBBABB', 3), [['6-7'], None]),
  ('control straight sets', ('AAAAAAAAAAAA', 3), [['6-0', '6-0'], 'A']),
  ('control in-progress set', ('AAAAAAB', 3), [['6-0', '0-1'], None]),
  ('control empty', ('', 5), [[], None]),
  ('regression: sets needed', ('BABAAABBAAAABAAABAABBABBBBAAA', 3), [['6-4', '6-2'], 'A']),
  ('regression: sets needed',
   ('AAAAAAAABAAAAAAABAAAABAABBAAAAAABAABBAAABA', 5),
   [['6-0', '6-1', '6-1'], 'A']),
  ('variant scenario 1',
   ('BBBABBBAAABAAAAAAAAABABAAABAAAAAABABA', 3),
   [['1-6', '6-1', '6-0'], 'A']),
  ('variant scenario 2', ('BBAAAAAABABBABBABAAAAAAAAABAABBA', 3), [['6-2', '3-6', '6-0'], 'A'])]]
for label, args, expected in cases[N - 1]:
    check(label, run(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
control bagel set[['6-0'], None][['6-0'], None]Passed
boundary seven-five[['7-5'], None][['7-5'], None]Passed
boundary tiebreak set[['6-7'], None][['6-7'], None]Passed
control straight sets[['6-0', '6-0'], 'A'][['6-0', '6-0'], 'A']Passed
control in-progress set[['6-0', '0-1'], None][['6-0', '0-1'], None]Passed
control empty[[], None][[], None]Passed
regression: sets needed[['6-3', '1-2'], None][['6-3', '1-2'], None]Passed
regression: sets needed[['6-0', '6-4', '6-3'], 'A'][['6-0', '6-4', '6-3'], 'A']Passed
variant scenario 1[['4-5'], None][['4-5'], None]Passed
variant scenario 2[['6-1', '2-6'], None][['6-1', '2-6'], None]Passed

SHA-256 / eff08906d451645568b611bc3eba7a4c63a0206c10b1b4729429988caa8e90a0

Verification & scope

Stipulated, bounded toy contract stated in the contract field; not a claim of conformance with any governing body rulebook or operator house rules. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:50:25.856854+00:00.

Case digest / c1d46e16d1420d4301a3632e5fbbe70d91b1c7a9e363dca8c6d24687dcb1b971