Input values instead of predefined

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Hi I need to take user input instead of predefined values below. I know its "cin" but dont know in lists.

#include <iostream>
using namespace std;
 
/* Link list node */
struct Node {
   int data;
   struct Node* next;
   };
 
//delete first node in the linked list
Node* deleteFirstNode(struct Node* head)
{
   if (head == NULL)
   return NULL;
 
   // Move the head pointer to the next node
   Node* tempNode = head;
   head = head->next;
   delete tempNode;
 
   return head;
}
//delete last node from linked list
Node* removeLastNode(struct Node* head)
{
   if (head == NULL)
   return NULL;
 
   if (head->next == NULL) {
      delete head;
      return NULL;
   }
 
// first find second last node
Node* second_last = head;
while (second_last->next->next != NULL)
second_last = second_last->next;
 
// Delete the last node
delete (second_last->next);
 
// set next of second_last to null
second_last->next = NULL;
 
return head;
}
 
// create linked list by adding nodes at head
void push(struct Node** head, int new_data)
{
   struct Node* newNode = new Node;
   newNode->data = new_data;
   newNode->next = (*head);
   (*head) = newNode;
}
 
// main function
int main()
{
   /* Start with the empty list */
   Node* head = NULL;
 
   // create linked list
   push(&head, 2);
   push(&head, 4);
   push(&head, 6);
   push(&head, 8);
   push(&head, 10);
 
         Node* temp;
 
   cout<<"Linked list created "<<endl; for (temp = head; temp != NULL; temp = temp->next)
   cout << temp->data << "-->";
   if(temp == NULL)
   cout<<"NULL"<<endl;
 
       //delete first node
   head = deleteFirstNode(head);
   cout<<"Linked list after deleting head node"<<endl; for (temp = head; temp != NULL; temp = temp->next)
   cout << temp->data << "-->";
   if(temp == NULL)
   cout<<"NULL"<<endl;
 
      //delete last node
   head = removeLastNode(head);
   cout<<"Linked list after deleting last node"<<endl; for (temp = head; temp != NULL; temp = temp->next)
   cout << temp->data << "-->";
   if(temp == NULL)
   cout<<"NULL";
 
   return 0;
}

What I have tried:

.

<pre>#include <iostream>
using namespace std;
 
/* Link list node */
struct Node {
   int data;
   struct Node* next;
   };
 
//delete first node in the linked list
Node* deleteFirstNode(struct Node* head)
{
   if (head == NULL)
   return NULL;
 
   // Move the head pointer to the next node
   Node* tempNode = head;
   head = head->next;
   delete tempNode;
 
   return head;
}
//delete last node from linked list
Node* removeLastNode(struct Node* head)
{
   if (head == NULL)
   return NULL;
 
   if (head->next == NULL) {
      delete head;
      return NULL;
   }
 
// first find second last node
Node* second_last = head;
while (second_last->next->next != NULL)
second_last = second_last->next;
 
// Delete the last node
delete (second_last->next);
 
// set next of second_last to null
second_last->next = NULL;
 
return head;
}
 
// create linked list by adding nodes at head
void push(struct Node** head, int new_data)
{
   struct Node* newNode = new Node;
   newNode->data = new_data;
   newNode->next = (*head);
   (*head) = newNode;
}
 
// main function
int main()
{
   /* Start with the empty list */
   Node* head = NULL;
 
   // create linked list
   push(&head, 2);
   push(&head, 4);
   push(&head, 6);
   push(&head, 8);
   push(&head, 10);
 
         Node* temp;
 
   cout<<"Linked list created "<<endl; for (temp = head; temp != NULL; temp = temp->next)
   cout << temp->data << "-->";
   if(temp == NULL)
   cout<<"NULL"<<endl;
 
       //delete first node
   head = deleteFirstNode(head);
   cout<<"Linked list after deleting head node"<<endl; for (temp = head; temp != NULL; temp = temp->next)
   cout << temp->data << "-->";
   if(temp == NULL)
   cout<<"NULL"<<endl;
 
      //delete last node
   head = removeLastNode(head);
   cout<<"Linked list after deleting last node"<<endl; for (temp = head; temp != NULL; temp = temp->next)
   cout << temp->data << "-->";
   if(temp == NULL)
   cout<<"NULL";
 
   return 0;
}

Posted 10-Jan-22 5:38am

jasmeet singh 2021

Updated 10-Jan-22 5:44am

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Comments

jeron1 10-Jan-22 11:42am

Using a loop (while or for) that has data entry (cin) inside?

jasmeet singh 2021 10-Jan-22 11:44am

Linked list has to be from user input

jeron1 10-Jan-22 11:49am

OK, so have the user enter it, using a loop with cin.

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Richard MacCutchan · Answer 1 · 2022-01-10T05:44:00

Solution 1

Try this:

C++

int count = 0;
int value = 0;

cout << "Please enter the number of values: ";
cin >> count; // the number of values to be input below

while (count > 0)
{
    cout << "Please enter the next value: ";
    cin >> value; // get next value
                  // and push it into the list
    push(&head, value);
    count--;
}

Posted 10-Jan-22 5:44am

Richard MacCutchan

Comments

jasmeet singh 2021 10-Jan-22 15:12pm

Do I need to write this?
Node* head = NULL

Richard MacCutchan 10-Jan-22 15:23pm

Yes; the node list must be initialised before you add the first entry.

jasmeet singh 2021 10-Jan-22 15:29pm

many thanks

jasmeet singh 2021 10-Jan-22 18:52pm

Could you also help me in user input for STL list?

#include<iostream>
#include<list> // for list operations
using namespace std;

int main()
{
// initializing list of integers
list<int> list1={10,15,20,25,30,35};

// declaring list iterators
list<int>::iterator it = list1.begin();
list<int>::iterator it1 = list1.begin();

// incrementing the positions of iterators
advance(it,2);
advance(it1,5);

// printing original list
cout << "The original list is : ";
for (list<int>::iterator i=list1.begin(); i!=list1.end(); i++)
cout << *i << " ";

cout << endl;

// using erase() to erase single element
// erases 20
list1.erase(it);

// list after deletion 1 element
cout << "The list after deleting 1 element using erase() : ";
for (list<int>::iterator i=list1.begin(); i!=list1.end(); i++)
cout << *i << " ";

cout << endl;

it = list1.begin();

// incrementing the positions of iterators
advance(it,2);

// using erase() to erase multiple elements
// erases 25,30
list1.erase(it,it1);

// list after deletion of multiple elements
cout << "The list after deleting multiple elements using erase() : ";
for (list<int>::iterator i=list1.begin(); i!=list1.end(); i++)
cout << *i << " ";

cout << endl;

}

Richard MacCutchan 11-Jan-22 3:38am

Help you how? You have not explained your problem.

jasmeet singh 2021 11-Jan-22 3:45am

It was same as for linked list above - To have input from user instead of predefined list. But I managed to do it

jasmeet singh 2021 17-Jan-22 13:20pm

How to remove the highest value from the list?

Richard MacCutchan 18-Jan-22 3:49am

You first need to go through all the entries to find the one with the highest value. Once you have that it is a simple matter to link its parent and child nodes together to remove it.