Pass by Reference for Linked List
Hello,
I cant get my insert function to insert to the head of the list I dont think I'm passing the pointers correctly.
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#include <iostream>
using namespace std ;
struct list1 {
int data ;
list1 * next = NULL;
};
struct list2 {
int data ;
list2 * next = NULL ;
};
bool isList1Empty ( list1 * head ) ;
bool isList2Empty ( list2 * head ) ;
void printList1 ( list1 * head ) ;
void printList2 ( list2 * head ) ;
void insertList1 ( list1 ** head , int toInsert ) ;
void insertList2 ( list2 * head , int toInsert ) ;
int main () {
list1 * headptr1 = NULL ;
list2 * headptr2 = NULL ;
insertList1 ( & headptr1 , 5 ) ;
}
bool isList1Empty ( list1 * head ) {
if ( head == NULL )
return true ;
}
bool isList2Empty ( list2 * head ) {
if ( head == NULL )
return true ;
}
void printList1 ( list1 * head ) {
if (isList1Empty(head) == true)
cout << "List 1 Is Empty\n" ;
}
void printList2 ( list2 * head ) {
if (isList2Empty(head) == true)
cout << "List 2 Is Empty\n" ;
}
void insertList1 ( list1 * head , int toInsert ) {
if (isList1Empty(head) == true) {
list1 * newNode = new list1 ;
newNode->data = toInsert ;
head = newNode ;
cout << head->data << endl;
}
}
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The method you are calling on line 29 is:
void insertList1 ( list1 ** head , int toInsert ) ;
Which you have not yet defined/implemented
So would I just need a regular pointer or a pointer to a pointer?
I don't understand your question. You are calling this method:
void insertList1 ( list1 ** head , int toInsert ) ;
So you need to actually tell the program what to do when that method is called by putting some code inside the method body:
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void insertList1 ( list1 ** head , int toInsert )
{
// code goes here
}
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Here is what I implemented it with:
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void insertList1 ( list1 ** head , int toInsert ) {
if (isList1Empty(head) == true) {
list1 * newNode = new list1 ;
newNode->data = toInsert ;
(*head) = newNode ;
cout << head->data << endl;
}
}
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