Recursion

Thinking Recursively

The algorithms for computing the triangle area, the factorial function and the word permutations all work on the same principle.
- When working on a complex input, first solve the problem with a simpler input.
- Turn the simpler result into the result for the more complex unit.
One function calls another that works on an even simpler input until one function's input is so simple that it can compute the results without further help.
What's important is that you can focus on putting a solution together from the slightly simpler problem.