# An Introduction to Recursion: A Powerful Tool for Problem Solving in Programming

January 4, 2023โข372 words

Recursion is a way of solving a problem by breaking it down into smaller problems and solving those smaller problems first. Imagine you are trying to count the number of apples in a basket. One way you could do this is by counting each apple one by one. This would be a very simple way to solve the problem, but it might take a long time if there are a lot of apples.

A better way to solve this problem would be to use recursion. With recursion, you would first divide the basket of apples into smaller piles, and then count the number of apples in each smaller pile. Once you have counted all of the apples in the smaller piles, you can add up all of those numbers to get the total number of apples in the basket.

In programming, recursion is often used to solve problems that involve repeating a process or breaking a problem down into smaller pieces. Here is an example of a recursive function in Python that calculates the factorial of a number:

```
def factorial(n):
if n == 1:
return 1
else:
return n * factorial(n-1)
```

In this example, the function "factorial" takes a number as input and returns the factorial of that number. The factorial of a number is the product of that number and all of the numbers that come before it. For example, the factorial of 5 is 5 x 4 x 3 x 2 x 1, which is equal to 120.

The function uses recursion to solve the problem by calling itself with a smaller number (n-1) until it reaches the base case (n == 1). The base case is the point at which the function stops calling itself and returns a result. In this example, the base case is when n is equal to 1, because the factorial of 1 is always 1.

Recursion can be a powerful tool for solving problems, but it is important to make sure that the function has a base case and that it will eventually stop calling itself, or else it will run forever and cause an infinite loop. So, recursion is a very useful concept in programming and problem solving.

*courtesy of ChatGPT*