# What Is Recursion Data Structure?

//

Heather Bennett

A data structure is a way of organizing and storing data in a computer’s memory. One popular data structure is recursion, which allows a function to call itself repeatedly until a certain condition is met. Recursion can be a powerful tool in solving problems that can be broken down into smaller, similar subproblems.

## Understanding Recursion

Recursion works by breaking down a problem into smaller subproblems, solving each subproblem, and then combining the solutions to get the final result. It follows the concept of “divide and conquer”.

When designing algorithms using recursion, there are two key components:

• Base case: This is the condition that determines when the recursion stops. It acts as the exit point for the recursive function.
• Recursive case: This is where the function calls itself with a smaller or simpler input than before. It helps in breaking down the problem into smaller subproblems.

The base case prevents infinite recursion by providing a stopping condition. Without it, the recursive function would keep calling itself indefinitely.

## Example: Calculating Factorial

To illustrate how recursion works, let’s consider an example of calculating factorial.

The factorial of a non-negative integer n (denoted as n!) is the product of all positive integers less than or equal to n.

We can define the factorial function recursively as follows:

``````
function factorial(n) {
// Base case: factorial of 0 or 1 is 1
if (n === 0 || n === 1) {
return 1;
}

// Recursive case: multiply n with factorial(n-1)
return n * factorial(n - 1);
}
```
```

Let’s understand how the factorial function works with an example:

``````
factorial(5) = 5 * factorial(4)
= 5 * (4 * factorial(3))
= 5 * (4 * (3 * factorial(2)))
= 5 * (4 * (3 * (2 * factorial(1))))
= 5 * (4 * (3 * (2 * 1)))
= 120
```
```

As we can see, the function calls itself with smaller input until it reaches the base case. Then, it starts returning values in reverse order, multiplying them to get the final result.

## Pros and Cons of Recursion

• Simplicity: Recursive solutions are often simpler and more elegant compared to iterative solutions.
• Modularity: Recursion allows for modular code, as smaller subproblems can be solved independently.
• Flexibility: Recursive algorithms can handle problems with variable input sizes.

However, recursion also has some drawbacks:

• Performance Overhead: Recursive algorithms may have a higher memory usage and slower execution time compared to iterative algorithms.
• Potential Stack Overflow: If the depth of recursion becomes too large, it can cause a stack overflow error and crash the program.

## In Conclusion

Recursion is a powerful data structure that allows functions to call themselves to solve complex problems by breaking them down into smaller subproblems. It follows the divide and conquer approach, leveraging base cases and recursive cases to achieve the desired result. While recursion offers simplicity and modularity, it’s important to consider its potential performance overhead and the risk of stack overflow.