Binary Search on Rotated Arrays Preserves O(log n) Complexity

Binary Search on Rotated Arrays: Adapting Logarithmic Search to Broken Invariants Standard binary search requires sorted data. When an array is rotated (e.g., [4,5,6,7,0,1,2]), the sorted property breaks globally but persists locally — one half is always properly sorted. The adaptation: determine which half is sorted by comparing endpoints, then check if the target falls within that sorted range. This preserves O(log n) complexity despite the rotation disrupting global order. The Design Lesson: When invariants break, look for partial invariants. Here, global sorting is lost but local sorting remains. This "find the preserved property" approach applies broadly — searching in nearly-sorted data, handling corrupted indices with known structure, or working with time-series data with periodic gaps. The algorithm adapts to what guarantees still hold. Time: O(log n) | Space: O(1) #BinarySearch #AdaptiveAlgorithms #RotatedArrays #InvariantPreservation #Python #AlgorithmDesign #SoftwareEngineering

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