Binary Search Problems & Solutions

Binary Search: Problems and Variations for Interviews

Binary search appears in approximately 25% of coding interviews, making it the single most frequently tested algorithm. Beyond the basic sorted array search, there are 5+ advanced variations that interviewers love because they test both implementation precision and problem-reduction thinking.

Binary search reduces any monotonic search space from O(n) to O(log n). The key insight: if you can define a condition that is false for the first half and true for the second half (or vice versa), you can binary search it.

5 Binary Search Variations

1. Classic — Find target in sorted array
2. Lower/Upper Bound — Find first/last occurrence of target (bisect_left/bisect_right)
3. Rotated Sorted Array — Search in array rotated at unknown pivot
4. Search on Answer — Binary search on the answer space (e.g., "minimum maximum", "koko eating bananas")
5. 2D Matrix Search — Treat 2D matrix as flattened 1D sorted array

Implementation Tips

• Use inclusive bounds: left = 0, right = n - 1
• Avoid overflow: mid = left + (right - left) / 2
• Be precise with exit condition: while (left <= right) vs while (left < right)

Binary search pairs well with sorting algorithms and array patterns. Practice with AissenceAI's coding copilot.