# Recursion ## Categories Two general categories of recursion functions: 1. repeatedly execute a task 2. perform a calculation based on a subproblem ## Strategy Approach recursion with a top-down approach. Strategy (from [A Common-Sense Guide to Data Structures and Algorithms, Second Edition](https://pragprog.com/titles/jwdsal2/a-common-sense-guide-to-data-structures-and-algorithms-second-edition/) ) 1. Imagine the function you're writing has already been implemented 2. Identify the subproblem of the problem 3. See what happens when you call the function on the subproblem and go from there --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://monica-granbois.gitbook.io/cs-theory-and-problems/algorithms/recursion.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.