# Recursion Vs Iteration – Their Uses and differences

Before going to know about Recursion vs Iteration, their uses and difference, it is very important to know what they are and their role in a program and machine languages. So, let’s get started with the definitions of Recursion and Iteration.

## What is a Recursion?

In a computer programming language, Recursion is the process of calling a function by itself. You can be able to call the required function directly or indirectly. The function that is corresponding to the Recursion is called a recursive function. You can use recursion widely in computer science to solve complex problems. You can also be able to break this function down into simpler ones. It plays an important role when you are writing algorithms for a given problem statement.

The other important thing you need to know about recursion is that every recursive function contains a base condition in it. You can provide the solution to the base case and the solution to the bigger problem in terms of smaller problems. This is one of the best features of a recursion.

While you are writing a program, you can use the base condition to stop a recursive function from executing endlessly. This can be done once a pre-specified base condition is met and the function should know that it’s the right time to exit. must have a The presence of a base case in every recursive program is mandatory to make sure that the function will terminate at some point. If there is no base case, the program results in unexpected behavior. Thus, you must use the base case condition while you are writing a recursive program.

### Uses of a Recursion

Recursion is mostly used by programmers for solving problems by breaking them down into smaller, and repetitive problems. Usually, you can implement recursion on things that have many possible branches and also on the things that are too complex to use an iterative approach. For example, you can use recursion in searching through a file system.

To use the recursion function in your program, you must know the structure of a recursion. So, I suggest you follow the below steps when you write a program for any problem statement irrespective of the programming language used in your code.

The structure of a recursive program is as follows:

• The first step in a recursive program is Initializing the algorithm. Recursive programs often need a seed value to start with. Here, you can use a parameter passed to the function or you can provide a gateway function that is nonrecursive.
• Then you need to check whether the current values are matched with the base case or not because you have to process and return the value if they are not matched with the base case.
• Now, it’s time to redefine the answer in terms of a smaller or simpler sub-problem or sub-problems.
• Then, you have to run the algorithm on the sub-problem.
• Now, try to combine the results in the formulation of the answer.
• Finally, you need to return the results.

These are the steps you must follow while writing a recursive function in any programming language.

Now, we shall see how you will use the recursions in various programming languages like C, Java, and python.

Recursion in C programming language:

By looking at the below example, you will come to know how recursion is used in the C programming language.

Example:

#include <stdio.h>
int sum(int n);
int main()
{
int number, result;
printf("Enter a positive integer: ");
scanf("%d", &number);
result = sum(number);
printf("sum = %d", result);
return 0;
}
int sum(int n)
{
if (n != 0)
return n + sum(n-1);
else
return n;
}
The above recursion program gives you the following output:
Enter a positive integer:3
sum = 6

### Recursion in Java programming language:

If you look at the below example, you will come to know how recursion is used in the Java programming language. In this example, you have to add all of the numbers up to 10 using Recursion.

Example:

public class Javarecursion
{
public static void main(String[] args)
{
int result = sum(10);
System.out.println(result);
}
public static int sum(int k)
{
if (k > 0)
{
return k + sum(k - 1);
}
else {
return 0;
}
}
}

public class Javarecursion

### Recursion in python programming language

def factorial(x):
if x == 1:
return 1
else:
return (x * factorial(x-1))
N = 3
print("The factorial of", N, "is", factorial(N))

Generally, everything will have some pros and cons respectively. Now, let us see some of the advantages and disadvantages of using Recursion in programming.

### Advantages of using Recursion in programming:

1. You will be able to reduce the time complexity of the program with the help of a Recursion.
3. You can reduce the written time and debugging time of the program.
4. You can break down a complex task into simpler sub-problems using recursion.

### Dis-advantages of using Recursion in programming:

1. You will not be able to follow the logic behind recursion sometimes.
2. You need more memory to use recursion in your program.
3. You will face difficulties in using recursion because it is very slow.

## What is Iteration?

The process of using a set of instructions or structures in a repeated sequence is called an Iteration. You will have to use iteration a specified number of times or until you meet the required condition.

Here, you will be able to execute the set of statements only until the condition in the iteration statement is True. You will observe that the iteration will be terminated when the condition evaluates to be false. There is a control variable that defines the state of an Iteration in your program. A control variable is another important factor that you need to know while learning the Iteration. Using a control variable, you will be able to run a loop that is generally i or j in most cases. In case, if the condition variable is absent in the given statement,then it enters into a condition known as an infinite loop.

In general, you can find two types of iterations in the programming world. Let us know about them clearly. The following are the two types of iterations we have:

### 1. Count-controlled loops

With the help of count-controlled loops, you can iterate all the steps a specific number of times. But, before using this type of loop in your program, you must know the number of iterations that are going to take place in your program. You will be able to use them only when the number of iterations to take place is already known. Or else, you cannot use this type of loop in your program. A counter is used by the count-controlled loops so that they be able to keep track of how many times the set of commands has been repeated

You will use the For-Statement in order to execute the Count-controlled loops. This will help you to specify the starting point of the iteration. And it also finds the range that indicates how many times the program will iterate

Example of a Count Controlled Loop:

total = 0
for count in range (4):
number = int (input (“Type in a number: “))
total = total + number
print (“The total is: “)
print (total)

After executing the above example, you will observe that the program repeats 4 times. You should change the value ’4’ to the number of times preferred. This will help you to have a different number of repetitions.

### 2. Condition-controlled loops

You will use this type of Iteration method for iterating steps continuously until a condition is met. You can use this type of Iteration only when the number of iterations to take place is unknown. Because already you have studied that you need to use the count controlled loops when you know the number of iterations that are going to be taken place.

To know whether the condition is true or not, the algorithm tests the condition.  If true, Then the algorithm executes a command if the result after the test is true.  Or in case, if the algorithm goes back to step 1 it gives the result as fast and the program; will continue to go back until the condition becomes true. When you execute the Condition-controlled loops, you are supposed to use WHILE statements.

Example of a Condition Controlled Loop

total = 0
number = int (input (“Type in a number: “))
total = total + number
answer = input (“Any more numbers? yes/no “)
print (“The total is: “)
print (total)

After executing the above program, you will observe that the program iterates as many times as is necessary and will keep iterating as long as the condition is met.

You will also observe that a condition-controlled loop executes forever.  Hence, you will call this an infinite loop.  In an infinite loop, you need to ensure that a program runs forever so that you can use this in controlling a traffic light and other similar scenarios.

Hence, I conclude that these are the major differences between the usage of Recursion vs Iteration in programming. By reading this article, you will understand which one among recursion and iteration is better to use while you are writing a program in any language.

If you are learning coding and stuck with your coding assignments? Worry now, get expert coding help right now.

Scroll to Top