An offline algorithm is an algorithm that processes all input data at once, making decisions based on the complete dataset before producing any output.

Use an offline algorithm when:

1. You’re given the entire input up front and you’re allowed to process it all at once.
2. You can reorder, sort, or batch the input to optimize performance.
3. You’re solving problems like range queries, event merging, or multiple queries on static data.
4. You want to preprocess the input and answer many queries efficiently.