DSA Linked Lists Operations

🔗 DSA Linked Lists Operations – Complete Guide

(Traversal • Insertion • Deletion • Searching • Code Examples)

Linked List operations are core DSA topics and are asked very frequently in exams & interviews.
Below is a clear, step-by-step explanation with C++ example code.

1️⃣ Basic Linked List Node (C++ Structure)

2️⃣ Traversal Operation

(Visiting all nodes)

🔹 Logic

Start from head
Move using next pointer
Stop when NULL is reached

🔹 Code

⏱ Time Complexity

3️⃣ Insertion Operations

🔹 A) Insert at Beginning

Steps

Create new node
Point it to current head
Move head to new node

Code

⏱ O(1)

🔹 B) Insert at End

Steps

Traverse to last node
Attach new node

Code

void insertAtEnd(Node*& head, int value) {
Node* newNode = new Node();
newNode->data = value;
newNode->next = NULL;

if(head == NULL) {
head = newNode;
return;
}

Node* temp = head;
while(temp->next != NULL)
temp = temp->next;

temp->next = newNode;
}

void insertAtEnd(Node*& head, int value) {

Node* newNode = new Node();

newNode->data = value;

newNode->next = NULL;

if(head == NULL) {

head = newNode;

return;

}

Node* temp = head;

while(temp->next != NULL)

temp = temp->next;

temp->next = newNode;

}

⏱ O(n)

🔹 C) Insert at Specific Position

Code

⏱ O(n)

4️⃣ Deletion Operations

🔹 A) Delete from Beginning

⏱ O(1)

🔹 B) Delete from End

⏱ O(n)

🔹 C) Delete a Specific Value

void deleteValue(Node*& head, int value) {
if(head == NULL) return;

if(head->data == value) {
Node* temp = head;
head = head->next;
delete temp;
return;
}

Node* temp = head;
while(temp->next != NULL && temp->next->data != value)
temp = temp->next;

if(temp->next != NULL) {
Node* del = temp->next;
temp->next = del->next;
delete del;
}
}

void deleteValue(Node*& head, int value) {

if(head == NULL) return;

if(head->data == value) {

Node* temp = head;

head = head->next;

delete temp;

return;

}

Node* temp = head;

while(temp->next != NULL && temp->next->data != value)

temp = temp->next;

if(temp->next != NULL) {

Node* del = temp->next;

temp->next = del->next;

delete del;

}

⏱ O(n)

5️⃣ Searching Operation

🔹 Logic

Compare each node’s data with key.

🔹 Code

⏱ O(n)

6️⃣ Complete Example (All Operations Together)

#include <iostream>
using namespace std;

struct Node {
int data;
Node* next;
};

int main() {
Node* head = NULL;

insertAtBeginning(head, 10);
insertAtEnd(head, 20);
insertAtEnd(head, 30);
insertAtPosition(head, 15, 2);

traverse(head);
cout << endl;

deleteValue(head, 20);
traverse(head);

return 0;
}

#include <iostream>

using namespace std;

struct Node {

int data;

Node* next;

};

int main() {

Node* head = NULL;

insertAtBeginning(head, 10);

insertAtEnd(head, 20);

insertAtEnd(head, 30);

insertAtPosition(head, 15, 2);

traverse(head);

cout << endl;

deleteValue(head, 20);

traverse(head);

return 0;

}

Output

7️⃣ Time Complexity Summary

Operation	Time
Traversal	O(n)
Insert at Beginning	O(1)
Insert at End	O(n)
Insert at Position	O(n)
Delete from Beginning	O(1)
Delete from End	O(n)
Search	O(n)

Interview Tips

✔ Always update pointers carefully
✔ Handle head = NULL case
✔ Avoid memory leaks (delete)
✔ Draw memory diagrams in interviews

Final Summary

✔ Linked List operations modify node connections
✔ Insertion & deletion are efficient
✔ Traversal & search are sequential
✔ Pointer handling is the key
✔ Very important for DSA interviews

DSA Linked Lists Operations