If you’ve ever struggled with solving problems using recursion, or if you have to brush up your skills for an interview, this course is for you.

We'll start with the basics of what recursion is and why it’s important before diving into practicing solving actual questions. You’ll have access to detailed explanations and visualizations for each problem to help you along the way. 

By the time you have completed this course, you’ll be able to use all the concepts to solve complex real-world problems. We hope that through practicing recursion, you will be able to ace all recursion related questions in interviews at top tech companies.

Solving Problems with Recursion in Python

import node

class LinkedList: 
	def __init__(self) :
		self.head = None

	def append(self, new_data): 
		new_node = node.Node(new_data) 
		
		if self.head is None : # If head node is null 
			self.head = new_node 
			return

		last = self.head 
		while (last.next): 
			last = last.next
		last.next =  new_node # add new node to end of list

	def printList(self):
		temp = self.head
		while(temp):
			print(temp.data)
			temp = temp.next

class Node: 
	def __init__(self, data): 
		self.data = data 
		self.next = None


 import linkedList as l

def length(testVariable, head) :
	# Base case
	if (not head) :
		return 0
		
	# Recursive case
	else :
		return 1 + length(testVariable, head.next) 

# Driver Code
myLinkedList = l.LinkedList() 
myLinkedList.append(3) 
myLinkedList.append(4) 
myLinkedList.append(7) 
myLinkedList.append(11) 

print(length(myLinkedList, myLinkedList.head))

### Explanation

The **base case** for this problem will be the situation when a linked list contains **no nodes**. In this case, we will be returning $0$ as the length of the linked list.

For the **recursive case**, we will move the head pointer to its next node, i.e., `head.next`, and call another instance of the same function recursively. When this child function will return add $1$ to the result.

Our solution is based on the premise that:
$length \: of \: a \: linked \: list = 1 + length \: of \: a \: linked \: list \: with \: head \:pointer \: moved \:one \: step\: ahead$.

Let's dry run our code:


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In the next lesson, we have another challenge for you to solve.

## Explanation

The **base case** for this problem will be the situation when a linked list contains **no nodes**. In this case, we will be returning $0$ as the length of the linked list.

For the **recursive case**, we will move the head pointer to its next node, i.e., `head.next`, and call another instance of the same function recursively. When this child function will return add $1$ to the result.

Our solution is based on the premise that:
$length \: of \: a \: linked \: list = 1 + length \: of \: a \: linked \: list \: with \: head \:pointer \: moved \:one \: step\: ahead$.

Let's dry run our code:


This review provides a detailed analysis of the solution to find the length of a linked list.


Recursion Fundamentals

Iteration Vs. Recursion

Recursion with Numbers

Recursion with Strings

Recursion with Arrays

Recursion with Data Structures

Conclusion

Solution Review: Length of a Linked List

Solution: Using Recursion

Explanation