Small challenges.
Stronger problem solving.
352 programming exercises and projects, from interview patterns to practical data automation.
25 problems
01Repair an empty-input crashJavaScript · Read errors before changing codeEasyFree02Repair a missing-field crashJavaScript · Read errors before changing codeEasyFree03Repair division by zeroJavaScript · Read errors before changing codeEasyFree04Minimize a wrong-match reproductionJavaScript · Build a minimal reproductionEasyFree05Reduce a quantifier bugJavaScript · Build a minimal reproductionEasyFree06Separate prefix from containmentJavaScript · Build a minimal reproductionMediumPractice pack07Repair an inclusive endpointJavaScript · Find boundary and off-by-one errorsMediumPractice pack08Retain a short final chunkJavaScript · Find boundary and off-by-one errorsMediumPractice pack09Include the final adjacent pairJavaScript · Find boundary and off-by-one errorsMediumPractice pack10Repair unexpected input mutationJavaScript · Trace mutation and aliasingMediumPractice pack11Repair a shallow-copy leakJavaScript · Trace mutation and aliasingMediumPractice pack12Preserve valid falsy valuesJavaScript · Distinguish missing from falsyMediumPractice pack13Define the empty averageJavaScript · Distinguish missing from falsyMediumPractice pack14Report absent fields preciselyJavaScript · Distinguish missing from falsyMediumPractice pack15Reject booleans and partial numeric textJavaScript · Inspect coercion and comparison rulesMediumPractice pack16Repair lexical numeric sortingJavaScript · Inspect coercion and comparison rulesMediumPractice pack17Repair stale run stateJavaScript · Keep a regression for every repairMediumPractice pack18Repair deletion while iteratingJavaScript · Keep a regression for every repairMediumPractice pack19Make a tie rule deterministicJavaScript · Make results deterministicMediumPractice pack20Make grouped output stableJavaScript · Make results deterministicMediumPractice pack21Review an almost-correct interval helperJavaScript · Review plausible generated codeMediumPractice pack22Review an unstated winner policyJavaScript · Review plausible generated codeMediumPractice pack23Review unequal-length assumptionsJavaScript · Review plausible generated codeMediumPractice pack24Design tests for exact text semanticsJavaScript · Design assertions that distinguish wrong implementationsMediumPractice pack25Design a duplicate-sensitive assertionJavaScript · Design assertions that distinguish wrong implementationsMediumPractice pack
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