As we already know that linked lists are a dynamic data structure it is important to know how to insert an element as well. In the article given below we are seeing an approach on how to insert node at specific position in linked list in c
In this problem, we are given a singly linked list and a position. We have to insert a node at that specific position.
Understanding how to insert node at specific position in linked list.
The problem is quite simple. We just have to insert a node at a specific position in the given linked list.
Suppose the given list is 1 → 2 → 3 → 4 → 5, position = 2, and the data to be inserted is 6.
- According to the problem statement, we need to insert a node with value = 6 at 2nd position in the linked list.
- So, after adding the node with value = 6 at 2nd position in the given linked list, our resultant list will be 1 → 6 → 2→ 3 → 4 → 5.
Now, I think from the above example, the problem statement is clear.
So, now the main question is how we should approach this problem? What is the first thing that comes to mind when we talk about insertion at a specific position in linked list?
- List traversal, right? Yes. We are going to use list traversal for insertion at specific position in linked list.
Before moving further to the approach section, try to think of the approach by yourself.
- If stuck, no problem, we will thoroughly see how we can approach this problem in the next section.
Let’s move to the approach section.
Approach for insertion at specific position in linked list
Our approach is going to be pretty simple.
- We will simply traverse till (position -1)th node and add the newnode just after that node. Well, how will this work? Let us take an example.
- Suppose the list is 1 → 2 → 3, and we have to insert 4 at the 2nd position.
- Now, we will traverse (position -1) = (2-1) = 1 node and after traversing 1 node, we will be standing at 1.
- Now we will make 4 → next = 1 → next as we have to insert it after 1, and finally, 1 → next = 4 to link the nodes.
- By doing the above steps, 4 will be added at that specific position, and our resultant linked list will be: 1 → 4 → 2 → 3.
We can get a clearer look of approach by looking at the dry run.
Algorithm on how to insert node at specific position in linked list
- If the position where we are asked to insert pos is smaller than 1 or greater than the size of the list, it is invalid, and we will return.
- Else, we will make variable curr and make it point to the head of the list.
- Now we will run a for loop using curr to reach to the node at (pos-1)th position:
- The for loop will be: for(int i=1;inext;}
- After the termination of the above loop, curr will be standing at the (position – 1)th node.
- As explained above, we will simply make newnode → next = curr → next and curr → next = newnode.
- If the pos was equal to 1, we will make the head point to newnode as newnode will become the first node of the list.
Dry Run on how to insert node at specific position in linked list
Code Implementation on how to insert node at specific position in linked list
#include <stdio.h>
#include <stdlib.h>
struct Node {
int data;
struct Node* next;
};
int size = 0;
// Using this function we will be creating new nodes
struct Node* getNode(int data)
{
struct Node* newNode
= (struct Node*)malloc(
sizeof(struct Node));
newNode->data = data;
newNode->next = NULL;
return newNode;
}
// Using this function we will insert the newnode at the specific position
void insertAtPosition(struct Node* head, int pos, int data)
{
if (pos < 1 || pos > size + 1)
printf( "Invalid position!\n" );
else {
struct Node *curr=head;
for(int i=1;i<pos-1;i++) curr="curr-">next;
struct Node* temp=getNode(data);
temp->next=curr->next;
curr->next=temp;
if(pos=1)
head=temp;
size++;
}
}
// Using this function we will print the linked list
void printList(struct Node* head)
{
while (head != NULL) {
printf("%d ",head->data);
head = head->next;
}
printf("\n");
}
// Driver function
int main()
{
struct Node* head = NULL;
head = getNode(1);
head->next = getNode(2);
head->next->next = getNode(3);
head->next->next->next = getNode(4);
head->next->next->next->next = getNode(5);
size = 5;
printf("Linked list before insertion: ");
printList(head);
int data = 6, pos = 2;
insertAtPosition(head, pos, data);
printf("Linked list after insertion of 6 at position 2: ");
printList(head);
return 0;
}
#include <bits stdc++.h="">
using namespace std;
// Node structure of a singly linked list node
struct Node {
int data;
struct Node* next;
};
int size = 0;
// Using this function we will be creating new nodes
Node* getNode(int data)
{
Node* newNode = new Node();
newNode->data = data;
newNode->next = NULL;
return newNode;
}
// Using this function we will insert the newnode at the specific position
void insertAtPosition(Node* head, int pos, int data)
{
if (pos < 1 || pos > size + 1)
cout << "Invalid position!" << endl;
else {
Node *curr=head;
for(int i=1;i<pos-1;i++) {="" curr="curr-">next;
}
Node* temp=getNode(data);
temp->next=curr->next;
curr->next=temp;
if(pos=1)
head=temp;
size++;
}
}
// Using this function we will print the linked list
void printList(struct Node* head)
{
while (head != NULL) {
cout << " " << head->data;
head = head->next;
}
cout << endl;
}
// Driver function
int main()
{
Node* head = NULL;
head = getNode(1);
head->next = getNode(2);
head->next->next = getNode(3);
head->next->next->next = getNode(4);
head->next->next->next->next = getNode(5);
size = 5;
cout << "Linked list before insertion: ";
printList(head);
int data = 6, pos = 2;
insertAtPosition(head, pos, data);
cout << "Linked list after insertion of 6 at position 2: ";
printList(head);
return 0;
}
public class PrepBytes {
// Structure of a singly linked list node
static class Node {
public int data;
public Node nextNode;
public Node(int data) {
this.data = data;
}
}
// Function to create a new node and return
static Node GetNode(int data) {
return new Node(data);
}
// Function to insert an element at a specified index
static Node InsertAtPos(Node headNode, int position, int data) {
Node head = headNode;
if (position < 1)
System.out.print("Invalid position");
if (position == 1) {
Node newNode = new Node(data);
newNode.nextNode = headNode;
head = newNode;
} else {
for(int i=1;i<position - 1;i++)
{
headNode=headNode.nextNode;
}
Node newNode= new Node(data);
newNode.nextNode=headNode.nextNode;
headNode.nextNode=newNode;
}
return head;
}
// Function to print the list
static void PrintList(Node node) {
while (node != null) {
System.out.print(node.data);
node = node.nextNode;
if (node != null)
System.out.print(",");
}
System.out.println();
}
// Driver function
public static void main(String[] args) {
Node head = GetNode(1);
head.nextNode = GetNode(2);
head.nextNode.nextNode = GetNode(3);
head.nextNode.nextNode.nextNode = GetNode(4);
head.nextNode.nextNode.nextNode.nextNode = GetNode(5);
System.out.print("Linked list before insertion: ");
PrintList(head);
int data = 6, pos = 2;
head = InsertAtPos(head, pos, data);
System.out.print("Linked list after" + " insertion of 6 at position 2: ");
PrintList(head);
}
}
# A linked list Node
class Node:
def __init__(self, data):
self.data = data
self.nextNode = None
# function to create and return a Node
def getNode(data):
newNode = Node(data)
return newNode
# function to insert a Node at required position
def insertPos(headNode, position, data):
head = headNode
if (position < 1):
print("Invalid position!")
if position == 1:
newNode = Node(data)
newNode.nextNode = headNode
head = newNode
else:
while (position != 0):
position -= 1
if (position == 1):
newNode = getNode(data)
newNode.nextNode = headNode.nextNode
headNode.nextNode = newNode
break
headNode = headNode.nextNode
if headNode == None:
break
if position != 1:
print("position out of range")
return head
def printList(head):
while (head != None):
print(' ' + str(head.data), end = '')
head = head.nextNode
print()
if __name__=='__main__':
head = getNode(1)
head.nextNode = getNode(2)
head.nextNode.nextNode = getNode(3)
head.nextNode.nextNode.nextNode = getNode(4)
head.nextNode.nextNode.nextNode.nextNode = getNode(5)
print("Linked list before insertion: ", end='')
printList(head)
data = 6
position = 2
head = insertPos(head, position, data)
print("Linked list after insertion of 6 at position 2: ", end = '')
printList(head)
Output:
Linked list before insertion: 1,2,3,4,5
Linked list after insertion of 6 at position 2: 1,6,2,3,4,5
Time Complexity: O(n), as list traversal is needed.
Conclusion
So, in this article, we have tried to explain how to insert node at specific position in linked list using an easy and efficient approach. We understood the algorithm and the implementation of code for the better understanding.If you want to solve more questions on Linked List, which are curated by our expert mentors at PrepBytes, you can follow this link .
FAQs
- How can a loop be terminated?
- In a linked list what is a node?
- Is the head be considered as the node in the linked list?
- What is a struct * node in linked list?
A break statement exits a for loop or a while loop and after that we can use continue to go through with the other code except the loop which has terminated.
A node is a collection of two parts. One is data part which stores the value and the other part which stores the link to the next node.
As head in a linked list is the reference to the first node. So, the head is not considered as a node.
It is the representation of a node which consists the first part as the data and next part as the pointer, which stores the address of next node.