C++ Linked List Exercises: Insert a node at any position of a Singly Linked List
C++ Linked List: Exercise-9 with Solution
Write a C++ program to insert a new node at any position of a Singly Linked List.
Test Data:
Original list:
7 5 3 1
Position: 1, Value: 12
Updated list:
12 7 5 3 1
Position: 4, Value: 14
Updated list:
12 7 5 14 3 1
Position: 7, Value: 18
Updated list:
12 7 5 14 3 1 18
Sample Solution:
C++ Code:
#include <iostream>
using namespace std;
struct Node
{
int num;
Node *next;
}; //node constructed
int size = 0;
void insert(Node** head, int num){
Node* new_Node = new Node();
new_Node->num = num;
new_Node->next = *head;
*head = new_Node;
size++;
}
// method to insert at a given position
void insert_Position(int pos, int data, Node** head)
{
Node* new_node = new Node();
new_node->num = data;
new_node->next = NULL;
// Invalid positions
if(pos < 1 || pos > size + 1)
printf("Invalid\n");
// inserting first node
else if(pos == 1){
new_node->next = *head;
*head = new_node;
size++;
}
else
{
Node* temp = *head;
// traverse till the current (pos-1)th node
while(--pos > 1){
temp = temp->next;
}
new_node->next= temp->next;
temp->next = new_node;
size++;
}
}
//Display all nodes
void display_all_nodes(Node* node)
{
while(node!=NULL){
cout << node->num << " ";
node = node->next;
}
}
int main()
{
Node* head = NULL;
insert(&head,1);
insert(&head,3);
insert(&head,5);
insert(&head,7);
cout << "Original list:\n";
display_all_nodes(head);
int pos = 1, value = 12;
cout << "\n\nPosition: " << pos << ", Value: " << value;
insert_Position(pos, value, &head);
cout << "\nUpdated list:\n";
display_all_nodes(head);
pos = 4, value = 14;
cout << "\n\nPosition: " << pos << ", Value: " << value;
insert_Position(pos, value, &head);
cout << "\nUpdated list:\n";
display_all_nodes(head);
pos = 7, value = 18;
cout << "\n\nPosition: " << pos << ", Value: " << value;
insert_Position(pos, value, &head);
cout << "\nUpdated list:\n";
display_all_nodes(head);
cout<<endl;
return 0;
}
Sample Output:
Original list: 7 5 3 1 Position: 1, Value: 12 Updated list: 12 7 5 3 1 Position: 4, Value: 14 Updated list: 12 7 5 14 3 1 Position: 7, Value: 18 Updated list: 12 7 5 14 3 1 18
Flowchart:


CPP Code Editor:
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Previous C++ Exercise: Get Nth node in a Singly Linked List.
Next C++ Exercise: Delete first node of a Singly Linked List.
What is the difficulty level of this exercise?
C++ Programming: Tips of the Day
C++: const reference, before vs after type-specifier
No difference as const is read right-to-left with respect to the &, so both represent a reference to an immutable Fred instance.
Fred&const would mean the reference itself is immutable, which is redundant; when dealing with const pointers both Fred const* and Fred* const are valid but different.
It's a matter of style, but using const as a suffix since it can be applied consistently including const member functions.
Ref: https://bit.ly/3NmkTS7
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