Swap Nodes in Pairs 🎯

Welcome to an exciting journey through the world of Data Structures and Algorithms! Today, we're going to learn about swapping nodes in pairs, a fundamental concept that will help you understand and solve complex problems.

Understanding Linked Lists 📝

Before we dive into swapping nodes, let's quickly review linked lists, a common data structure we'll be working with. A linked list is a sequence of data elements, called nodes, linked using pointers. Each node contains a data part and a reference (or link) to the next node in the sequence.

python

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

Swapping Nodes in Pairs 💡

Now, let's focus on our main topic: swapping nodes in pairs. This technique is useful when you need to rearrange the order of elements in a linked list.

The Algorithm 📝

Initialize two pointers, current and next, both pointing to the head of the linked list.
Create a third pointer, temp, to help us temporarily store node references.
Swap the data of the nodes linked to current and next.
Move the current pointer two steps forward by updating it as current = current.next.next.
Move the next pointer one step forward by updating it as next = next.next.
Repeat steps 3-5 until the current pointer reaches the end of the linked list (when current.next is None).

Implementation 💡

Here's a complete implementation of the algorithm in Python:

python

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

def swapPairs(head):
    if head is None or head.next is None:
        return head

    current = head
    next_node = current.next
    temp = next_node.next

    current.next = next_node.next
    next_node.next = current.next.next
    next_node.next.next = next_node

    current.next = next_node

    current = current.next.next

    while current is not None:
        next_node = current.next
        temp = next_node.next

        current.next = next_node.next
        next_node.next = current.next.next
        next_node.next.next = next_node

        current.next = next_node
        current = current.next.next

    return head

# Testing the function
node1 = Node(1)
node2 = Node(2)
node3 = Node(3)
node4 = Node(4)

node1.next = node2
node2.next = node3
node3.next = node4

result = swapPairs(node1)

while result is not None:
    print(result.data)
    result = result.next

Quiz 🎯

Question: What does the swapPairs function do?

A: It finds the maximum element in a linked list B: It swaps nodes in pairs in a linked list C: It removes duplicates from a linked list Correct: B Explanation: The swapPairs function swaps nodes in pairs in a linked list.