#import <iostream>
#import <string>
#include <fstream>

using namespace std;

//The phonebook itself.
class Book
{
	public:
	int people;
	
	//The information for a person.
	class Person
	{
		public:
		string firstname, lastname, phonenumber;
	};
	
	//Returns 1 if Person1 comes before Person2, 2 if Person2 comes before Person1, and -1 if they are the same.
	int Compare(Person Person1, Person Person2)
	{
		for(int i=0; i<Person1.lastname.length() && i<Person2.lastname.length();i++){
			if(Person1.lastname.at(i)<Person2.lastname.at(i))
				return 1;
			if(Person2.lastname.at(i)<Person1.lastname.at(i))
				return 0;
		}
		if(Person1.lastname.length()<Person2.lastname.length())
			return 1;
		if(Person2.lastname.length()<Person1.lastname.length())
			return 0;
		for(int i=0; i<Person1.firstname.length();i++) && i<Person2.lastname.length()
{
			if(Person1.firstname.at(i)<Person2.firstname.at(i))
				return 1;
			if(Person2.firstname.at(i)<Person1.firstname.at(i))
				return 0;
		}
		if(Person1.firstname.length()<Person2.firstname.length())
			return 1;
		if(Person2.firstname.length()<Person1.firstname.length())
			return 0;
		return -1;
	}
	
	struct Node
	{
		Node* parent;
		Node* left;
		Node* right;
		Person item;
	};
	
	Node* root;
	
	Book()
	{
		root=NULL;
	}
	
	//The interface of the phonebook.
	class UserInterface
	{
		
	};
	
	//Adds a person’s name (first and last) and phone number to the phone book.
	void Add(string firstname, string lastname, string phonenumber)
	{
		cout << "Adding carl"<<endl;
		Person carl;
		carl.firstname = firstname;
		carl.lastname = lastname;
		carl.phonenumber = phonenumber;
		people++;
		Node newperson;
		Node* parent;
		newperson.item=carl;
		if(root==NULL){
			newperson.parent=NULL;
			newperson.left=NULL;
			newperson.right=NULL;
			root = &newperson;
		}else{
			parent=ParentFinder(&newperson,root);
			if(Compare((&newperson)->item,parent->item){
				parent->left=&newperson;
			}else{
				parent->right=&newperson;
			}
		}
	}
	
	//Find which node should parent the new node.
	Node* ParentFinder(Node* kid, Node* areyoumymommy)
	{
		if(Compare(kid->item,areyoumymommy->item)==1){
			if(areyoumymommy->left!=NULL){
				return ParentFinder(kid, areyoumymommy->left);
			}else{
				return areyoumymommy;
			}
		}else if(Compare(kid->item,areyoumymommy->item)==0){
			if(areyoumymommy->right!=NULL){
				return ParentFinder(kid, areyoumymommy->right);
			}else{
				return areyoumymommy;
			}
		}
	}

	//Deletes a given person’s phone number, given only the name. 
	void Delete(string firstname, string lastname)
	{
		
		delete FindNodeName(firstname, lastname);
		people--;
	}
	
	//Finds the node for a given name.
	Node* FindNodeName(string firstname, string lastname)
	{
		Person nonum;
		Node* cur=root;
		nonum.firstname=firstname;
		nonum.lastname=lastname;
		nonum.phonenumber="555-5555";
		int a;
		while(a!=-1){
			a=Compare(nonum,cur->item);
			if(a==0){
				cur=cur->left;
			}else if(a==1){
				cur=cur->right;
			}
		}
		return cur;
	}

	//Locates a person’s phone number, given only the person’s name.
	string Find(string firstname, string lastname)
	{
		Node* pers=FindNodeName(firstname,lastname);
		return pers->item.phonenumber;
	}

	//Changes a persons phone number given the person’s name and new phone number.
	void Change(string firstname, string lastname, string phonenumber)
	{
		Node* pers=FindNodeName(firstname,lastname);
		pers->item.phonenumber=phonenumber;
	}

	//Displays (dumps) entire phone book in alphabetical order.  
	void Display(Node* rt)
	{
		ofstream phonebookout;
		phonebookout.open("Phonebook.txt");
		if (rt != NULL) {
           phonebookout << rt->item.lastname << ", " << rt->item.firstname << ":" << rt->item.phonenumber << "/n";      // Print the root item.
           Display( rt->left );    // Print items in left subtree.
           Display( rt->right );   // Print items in right subtree.
        }
		phonebookout.close();
	}

	//Quits the application, after first saving the phone book in a text file.
	void Quit()
	{
		Display(root);
		exit(1);
	}
};

int main()
{
	cout << "a" << endl;
	Book sefer=Book();
	if(sefer.root==NULL)
		cout << "b" << endl;
	sefer.Add("Josh", "Ellis", "941-7495");
	sefer.Add("Jo", "Ellis", "910-7495");
	sefer.Add("Xander", "Ellis", "922-7495");
	sefer.Add("Xander", "Ell", "922-9574");
	sefer.Add("Josh", "Xzqxiuz", "911");
	sefer.Add("Bobby", "Robertson", "902-7549");
}

Getting a seg fault during our add function. Its comparing the second persons name to itself. Can you help?

Try to find out on exactly which line the segfault occurs. Then check if the variables on that line have been initialized properly before the function is called.

sefer was declared but never initialized (you didn't allocate memory for it)
try using: Book serfer=new Book();

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