Linked List search Operations

[jack1414]

So here I've got a linked list that reads in person data from a file(ss_number, dob, fname, lname, state of residence), then creates a linked list of states and with a linked list of the people who reside in that state inside each state. I can perform a number of operations not shown here. However now I'm trying to find and print the youngest or oldest person from any state that the user inputs, however my print_oldest_or_youngest function prints just some random person from that state and gives me a seg fault, any help solving this problem would be greatly appreciated

-Heres one of 1000 lines from the file
10081957 101440980 Betty Lamprey NY //dob(DD/MM/YYYY) ss_number Fname Lname State of residence)

#include <iostream>
#include <string>
#include <string.h>
#include <fstream>
using namespace std;



struct person
{
    int dob,ss_number,year,month,day;
    string fname, lname,state;
    bool isstate;
    
    person()
    { year = dob%10000;
         month = (dob/10000)%100;
         day = dob/1000000;}
    person(int a, int b, string c, string d, string e)
    {dob=a; ss_number=b; fname=c; lname=d; state=e; isstate=false;
        }
    void print()
    {
        cout<<dob<<" "<<ss_number<<" "<<fname<<" "<<lname<<" "<<state<<endl;
    }
    
};

template<typename T>struct Link
{
    T*data;
    Link*next;
    
    Link()
    {}
    Link(T*a,Link<T>*C=NULL)
    {
        data=a;
        next=C;
        
    }
    ~Link()
    {delete next;}
    
};
template<typename T>
struct List
{
    Link<T>*Head,*tail;
    int count;
    List(Link<T>*h=NULL, Link<T>*t=NULL)
    {
        Head=h;
        tail=t;
        
    }
    ~List()
    { delete Head;}
    
    void add(T*object)
    {
        {   if (Head == NULL && tail == NULL)
        {   Link<T> * newlink = new Link<T>(object);
            Head = newlink;
            tail = Head;  }
        else
        {   Link<T> * newlink = new Link<T>(object);
            tail->next = newlink;
            tail=newlink;} }
    }

   




    void print_oldest_or_youngest(string state)
    {
        Link<T>*printS=Head;
        //T*S=NULL;   //printS is a link with type state
        
        while(printS!=NULL)
        {
            if(printS->data->sname == state)
            {
                cout << "SEARCH RESULTS FOR STATE: \n" << "Name: " << state <<
                "\n\n";
                
                string a;
                
                cin>>a;
                Link<person>*temp=printS->data->P->Head;
                while(temp!=NULL)
                {
                    if(a=="youngest")
                        find_youngest();
                    else
                        find_oldest();
                    
                    temp=temp->next;
                    temp->data->print();
                    break;}
                
            }
            printS = printS->next;
        }
        
    }
    
    person* find_youngest ()
    {
        Link<person> *temp=Head->data->P->Head;
        int youngY=0;
        int youngM=0;
        int youngD=0;
        person*hold=NULL;
        while(temp!=NULL)
        {
            if(temp->data->year<youngY)
            {
                youngY=temp->data->year;
                hold=temp->data;
                temp=temp->next;
            }
            else if(temp->data->year==youngY)
            {
                if(temp->data->month<youngM)
                {
                    youngM=temp->data->month;
                    hold=temp->data;
                    temp=temp->next;
                }
                else if(temp->data->month==youngM)
                {
                    if(temp->data->day<youngD)
                    {
                        youngD=temp->data->day;
                        hold=temp->data;
                        temp=temp->next;
                    }
                    else temp=temp->next;
                }
                else temp=temp->next;
            }
            else temp=temp->next;
        }
        return hold;
    }
   person* find_oldest()
    {
        Link<person> *temp=Head->data->P->Head;
        int youngY=0;
        int youngM=0;
        int youngD=0;
        person*hold=NULL;
        while(temp!=NULL)
        {
           if(temp->data->year>youngY)
           {
               youngY=temp->data->year;
               hold=temp->data;
               temp=temp->next;
           }
            else if(temp->data->year==youngY)
            {
                if(temp->data->month>youngM)
                {
                    youngM=temp->data->month;
                    hold=temp->data;
                    temp=temp->next;
                }
                else if(temp->data->month==youngM)
                {
                    if(temp->data->day>youngD)
                    {
                        youngD=temp->data->day;
                        hold=temp->data;
                        temp=temp->next;
                    }
                    else temp=temp->next;
                }
                else temp=temp->next;
            }
            else temp=temp->next;
        }
        //cout<<temp->data->fname;
        return hold;
    }
    
    };
struct state
{
    string sname;
    List<person>*P;
    bool isstate;
    state()
    {
        //        P=new person[3000];
    }
    state(string a,List<person> *x)
    {sname=a;
        P=x;
        isstate=true;}
    void print()
    {
        cout<<sname<<endl;
    }
};

List<state>*read_file(string file)//reads file, creates people and states and put people in their states
{
    List<state>* newlist=new List<state>();
        //        Link<T> * head=NULL;
    //        Link<T> * temp=NULL;
    ifstream fin;
    fin.open("data.txt");
    if (fin.fail())
        cout<<"file not found\n";
    if (!fin.fail())
    {
        while(true)
        {
            int a,b;
            string c,d,sn;
            fin>>a>>b>>c>>d>>sn;
            if (fin.fail())break;
            person * p=new person(a,b,c,d,sn);
            Link<state>*temp=newlist->Head;
            while(true)
            {
                if(temp==NULL)
                {
                    state*s=new state(sn,new List<person>());
                      newlist->add(s);
                    temp=newlist->tail;
                    temp->data->P->add(p);
                    
                  
                    break;
                }
                
                if(temp->data->sname == sn)
                {
                    temp->data->P->add(p);
                    break;
                }
                temp=temp->next;
            }
        }
    }
    else
        cout<<"Can't open file";
    fin.close();
    return newlist;
}

int main()
{
    person P;
    string a,b,c;
    cout<<"What file would you like to read in"<<endl;
    
    cin>>a;
   
List<state> *B= read_file(a);
   
  
    
    

    B->print_oldest_or_youngest(f);
   

    //B->find_oldest();
    
 
    
    return 0;
}