What will binary search return if the target is not found in the list?

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Question reminder: What will binary search return if the target is not found in the list?
Option 1: The first element. Explanation: Returning the first element would be incorrect because binary search only returns an index or value when it matches the target; locating the first element implies a successful find, not a failure to locate.
Option 2: The smallest element. Explanation: Returning the smallest element is irrelevant to the search outcome. Binary search does not report a boundary element as a signal of failure; it should locate the target or indicate its absence.
Option 3: -1 or some indication of failure. Explanation: This is the conventional signal for “not found” in many binary search implementations: the search returns a sentinel value such as -1 or an equivalent failure indicator when the target is absent from the list. This aligns with the expectation that no valid index corresponds to the target.
Option 4: The largest element. Explanation: Returning the largest element would incorrectly imply that the target was found at the end of the list, which is not the case if the target is missing. It misrepresents the search result.
Option 5: The closest element. Explanation: Some algorithms may aim to approximate or find the nearest value, but standard binary search either finds the exact match or returns a not-found indication; it does not guarantee the closest element as a result.
Option 6: Zero. Explanation: Zero as a return value would suggest either a valid index of the first element or a special-case convention, but by itself it does not reliably signal failure across all implementations; many languages use -1 for not found, not 0. It's not a universal not-found signal.
Overall, when the target is not present, the expected behavior is to return a not-found indicator such as -1 or another explicit failure signal, rather than any of the other listed options.

IS 4485-001 Fall 2025 Final Exam

What will binary search return if the target is not found in the list?

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