Big O notation
Mathematical notation describing algorithm performance scaling with input size. Big O expresses upper bounds on time/space complexity, ignoring constants. This notation enables complexity comparison without implementation details.
Real World
Netflix's recommendation engine must process 230 million users — choosing an O(n log n) algorithm over O(n²) is the difference between results in seconds versus days.
Exam Focus
When asked to 'state' Big O, give only the dominant term — drop constants and lower-order terms like 3n+5 becoming O(n).
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