Question

this is my linkedlist and to insert a new element in it , however i want it to be user entered linkedlist

#include <bits/stdc++.h> using namespace std;    // A linked list Node struct Node {     int data;     struct Node* next; };    // Size of linked list int size = 0;    // function to create and return a Node Node* getNode(int data) {     // allocating space     Node* newNode = new Node();        // inserting the required data     newNode->data = data;     newNode->next = NULL;     return newNode; }    // function to insert a Node at required position void insertPos(Node** current, int pos, int data) {     // This condition to check whether the     // position given is valid or not.     if (pos < 1 || pos > size + 1)         cout << "Invalid position!" << endl;     else {            // Keep looping until the pos is zero         while (pos--) {                if (pos == 0) {                    // adding Node at required position                 Node* temp = getNode(data);                    // Making the new Node to point to                 // the old Node at the same position                 temp->next = *current;                    // Changing the pointer of the Node previous                 // to the old Node to point to the new Node                 *current = temp;             }             else               // Assign double pointer variable to point to the               // pointer pointing to the address of next Node               current = &(*current)->next;         }         size++;     } }    // This function prints contents // of the linked list void printList(struct Node* head) {     while (head != NULL) {         cout << " " << head->data;         head = head->next;     }     cout << endl; }    // Driver Code int main() {     // Creating the list 3->5->8->10     Node* head = NULL;     head = getNode(3);     head->next = getNode(5);     head->next->next = getNode(8);     head->next->next->next = getNode(10);        size = 4;        cout << "Linked list before insertion: ";     printList(head);        int data = 12, pos = 3;     insertPos(&head, pos, data);     cout << "Linked list after insertion of 12 at position 3: ";     printList(head);        // front of the linked list     data = 1, pos = 1;     insertPos(&head, pos, data);     cout << "Linked list after insertion of 1 at position 1: ";     printList(head);        // insetion at end of the linked list     data = 15, pos = 7;     insertPos(&head, pos, data);     cout << "Linked list after insertion of 15 at position 7: ";     printList(head);        return 0; }

Answer 1

Not sure if just linkedlist is user-entered or the insertion is also user-specified. Both of them implemented, please change the insertion part to original if it is not required. Hope it helps!

The input is assuming the linked list data to be in a single line and the next lines are input for insertion in linkedlist.

The edited code is in bold.

Code:

#include <bits/stdc++.h>
using namespace std;

// A linked list Node
struct Node {

int data;
struct Node* next;

};

// Size of linked list
int size = 0;

// function to create and return a Node
Node* getNode(int data)
{

// allocating space
Node* newNode = new Node();

// inserting the required data
newNode->data = data;

newNode->next = NULL;

return newNode;

}

// function to insert a Node at required position
void insertPos(Node** current, int pos, int data)
{

// This condition to check whether the
// position given is valid or not.

if (pos < 1 || pos > size + 1)
cout << "Invalid position!" << endl;
else {
  
// Keep looping until the pos is zero
while (pos--) {

if (pos == 0) {

// adding Node at required position
Node* temp = getNode(data);

// Making the new Node to point to
// the old Node at the same position
temp->next = *current;

// Changing the pointer of the Node previous
// to the old Node to point to the new Node
*current = temp;

}
else
  
// Assign double pointer variable to point to the
// pointer pointing to the address of next Node
current = &(*current)->next;

}
size++;
}

}

// This function prints contents
// of the linked list
void printList(struct Node* head)
{

while (head != NULL) {
  
cout << " " << head->data;
head = head->next;

}
cout << endl;

}

// Driver Code
int main()
{

   // Creating an empty
   Node* head = NULL;
   int size, val;
   string line;
  
   cout<<"Enter size of linked list: ";
   cin>>size;
  
   // pass the iterator value as the position
   // at which number is to be inserted
   for(int i=1;i<=size;i++) {
  
       cin>>val;   // input element
       insertPos(&head, i, val);
   }
  
   cout << "Linked list before insertion: ";
   printList(head);
  
   // insertion part-----------------------------------------------------------
   int data, pos;
  
   while(true) {
   // ask user if they want to insert a number
   cout<<"Enter y|Y if data is to be inserted, otherwise enter anything: ";
   cin>>line;
  
   // insertion
   if(line == "y" || line == "Y") {
   cout<<"Enter data and position: ";
   cin>>data>>pos;
   // insert element
   insertPos(&head, pos, data);
  
   cout << "Linked list after insertion of "<<data<<" at position "<<pos<<": ";
   printList(head);
   } else {
   // come out of the loop if insertion is completed
   break;
   }
   }
  
   return 0;
  
}

Sample Output:

Code snippet screenshot: