When to Use

Look for these signals in the problem:

• "Sorted array" explicitly mentioned: Classic binary search directly applies. Even if not finding exact values, sorted order enables halving.
• "Find minimum/maximum that satisfies condition": Binary search on the answer space.

If you can verify a candidate answer in $O(n)$, search the range in $O(\log n)$.

• "Rotated sorted array": Modified binary search handles the rotation by checking which half is properly sorted.
• "Find boundary" or "first/last occurrence": Binary search variants find transition points between valid and invalid regions.