What is Recursion? Explain Recursion with the help of an example. State the advantages and disadvantages of Recursion.

Answer:

Recursion is a programming concept where a function calls itself directly or indirectly. It is used to solve problems that can be broken down into smaller, simpler problems of the same kind. The process of solving the problem is to solve the smaller problem and then combine the solutions to solve the original problem.

For example, let's consider the problem of calculating the factorial of a number. The factorial of a number n is the product of all positive integers less than or equal to n. It can be solved using recursion in the following way:

def factorial(n):
    if n == 0 or n == 1:
        return 1
    else:
        return n * factorial(n - 1)

In the above code, the factorial function calls itself to calculate the factorial of a number. The base case is when n is 0 or 1, in which case the function returns 1. For any other value of n, the function calls itself with the argument n - 1.

The recursive call to factorial(n - 1) means "calculate the factorial of n - 1". This recursive call will continue until it reaches the base case, and then the results of each call are multiplied together to get the final result.

Advantages of Recursion:

1. Simplicity: Recursive functions make the code look clean and elegant.
2. Problem Solving: Recursion is very useful in solving data structure problems like Trees and Graphs.
3. Problem Decomposition: Recursion is good for problems where the task can be broken down into similar tasks of a smaller size, like sorting, searching, etc.

Disadvantages of Recursion:

1. Overhead: Recursive calls are expensive (inefficient) as they take up a lot of memory and time.
2. Stack Overflow: Too many recursive calls can lead to a stack overflow. The maximum limit for stack depth is dependent on the system.
3. Debugging: Debugging recursive functions can be difficult.

Advantages	Disadvantages
Simplicity	Overhead
Problem Solving	Stack Overflow
Problem Decomposition	Debugging

In conclusion, recursion is a powerful concept in programming, but it should be used judiciously considering its advantages and disadvantages.