Recursion allows codes to get more compact and efficient by calling a similar function inside a function. This is kind of similar to looping functions, however, there are a huge number of differences. Recursion makes coding programs or solutions much faster and simpler.

In data structures, recursion occurs when a function calls itself directly or indirectly. Recursion is typically used when a larger problem can be broken down into smaller, more manageable subproblems.

Recursion also offers code redundancy, making it much more efficient to read and maintain codes. Understanding recursion well can lead to true mastery over functional programming languages and empower programmers to code certain programs rapidly. Some problems are inherently recursive in nature, thus it is very valuable to know recursive functions to solve them faster.

Besides, recursion is valuable and compulsory in many problems related to advanced algorithms such as tree and graph traversal. Learning the applications of recursion in data structure and how to effectively use recursion to manipulate functions in various programs is the key to a great coding experience. In this article, we will cover the topic Recursion in Data structure: How Does it work & its Types.

**What is Recursion in Data Structure? **

A recursive data structure can be defined as a data structure that can be broken down into simple or miniature instances of itself. For example, trees are composed of small trees and leaf nodes while lists can contain smaller lists as their elements.

However, recursion in the data structure can be defined as a method through which problems are broken down into smaller sub-problems to find a solution. This is done by replicating the function on a smaller scale, making it call itself and then combining them together to solve problems.

Recursion provides a natural approach in declaring many algorithms and is very valuable in functional programming. Developers can effectively use recursion instead of loop functions such as “for loop” or “while loop”.

C++, PHP, Scala and functional __Javascript__ allow recursive functions or developers to write recursion operations. Every iterative problem can be solved through recursion and every recursive problem can be solved by an iterative approach. This is why the importance of recursion in the data structure is more stressed.

To understand the applications of recursion in data structure or programming, one must first understand a loop. For example, using C++, if we had to create a loop to display all the possible numbers between 14 and 20, then we would have to use the following codes:

```
for(int i=15; i<20; i++) {
cout << "Possible Number: " << i << endl;
}
```

It would display this as a result:

Possible Number: 15

Possible Number: 16

Possible Number: 17

Possible Number: 18

Possible Number: 19

This is possible as the loops repeat the function as long as the value of “i” is lesser than 20 due to the use of “for loop”. The starting value is “15” as it is the first number that comes after 14 and the “i++” declaration ensures that every time the loop is repeated, 1 is added to the value of “i”.

Now, let us use the same code to call a function:

```
void numberFunction(int i) {
cout << "Possible Number: " << i << endl;
}
int main() {
for(int i=15; i<20; i++) {
numberFunction(i);
}
}
```

When using recursion or recursive functions, we do not need to use “for loop” as the function will call itself. Now, let us recreate this same program using recursion in C++.

With recursion, we won’t need to use ‘for loop’ because we will set it up so that our function calls itself. Let’s recreate this same program, only this time we will do it without ‘for loop’. We will use a recursion loop instead like this:

```
void numberFunction(int i) {
cout << "Possible Number: " << i << endl;
i++;
if(i<20) {
numberFunction(i);
}
}
int main() {
int i = 15;
numberFunction(i);
}
```

The above codes show how a recursive function has been made by creating a single call to the “numberFunction” and then it calls itself repeatedly till “i” reaches the last number before 20.

Also read about - __Recursive Binary Search__

## 5 Important Recursion in Data Structure Methods

There are 5 important and effective recursion techniques used by programmers. They are as follows:

### Tail Recursion

While linear recursion is commonly used, tail recursion offers distinct advantages. In tail recursion, the recursive functions are called at the very end of the process.

### Binary Recursion

Binary recursion involves calling functions two times, instead of one after the other. This type of recursion is particularly useful for operations like merging and tree traversal.

### Linear Recursion

Linear recursion is the most widely adopted method. In this approach, functions call themselves in a straightforward manner and terminate when a specific condition is met. Essentially, it involves functions making one-time calls to themselves during execution.

### Mutual Recursion

Mutual recursion is where one function uses others recursively, leading to functions calling each other. This technique is handy when working with programming languages that don't readily support recursive function calls. In mutual recursion, initial conditions are used for one, several, or even all of the functions.

### Nested Recursion

Nested recursion is an exception that can't be easily converted into an iterative format. In this approach, recursive functions pass parameters as recursive calls, resulting in recursions within recursions.