What is recursion and when should I use it?

Answer 1

In the most basic computer science sense, recursion is a function that calls itself. Say you have a linked list structure:

struct Node {
    Node* next;
};

And you want to find out how long a linked list is you can do this with recursion:

int length(const Node* list) {
    if (!list->next) {
        return 1;
    } else {
        return 1 + length(list->next);
    }
}

(This could of course be done with a for loop as well, but is useful as an illustration of the concept)