// Demonstrate some list building code

public class BuildLists {

// Given a list of Psersons construct the corresponding list of names. 
// Iterative solution
//
public static MyList<String> PersonL2Names(MyList<Person> pl) {
    if (pl == null) return null;
    MyList<String> first = new MyList<String>();
    MyList<String> last = first;
    while (pl != null) {
       last.setValue(pl.getValue().getFirstName());
       if (pl.getNext() == null) return first;
       MyList<String> n = new MyList<String>();
       last.setNext(n);
       last = n;
       pl = pl.getNext();
     }
    return first;
  }


// Given a list of Psersons construct the corresponding list of names. 
// Recursive solution
//
public static MyList<String> PersonL2NamesB(MyList<Person> pl) {
    if (pl == null) return null;
    MyList<String> first = new MyList<String>();
    first.setValue(pl.getValue().getFirstName());
    first.setNext(PersonL2NamesB(pl.getNext()));
    return first;
  }

// From the list of Persons pl, destructively delte all persons of sex
// s
// // pl is a variable that works its way down the list
// 3 is used to find the next Person not of sex s after pl.
//
public static MyList<Person> deleteSex(MyList<Person> pl, Sexes s) {
    MyList<Person> d = pl;
    MyList<Person> willReturn = null;
    while (pl != null && pl.getNext() != null) {
        d = pl.getNext();
        while (d != null &&
               d.getValue().getSex() == s) // Find the next person not of sex s
           d = d.getNext();
        pl.setNext(d);
        if (willReturn == null)  // at the end, return the first element of
          if (pl.getValue().getSex() != s)  // the list, if that is the right
              willReturn = pl;              // sex
           else willReturn = d;  // else return the first Person of tright sex
        pl = d;                  // move pl up to d;       
       }
    return willReturn;
   }

public static void main(String args[]) {
    Person BarackObama= new Person("Barack", "Obama", Sexes.Male);
    Person MichelleObama= new Person("Michelle", "Obama", Sexes.Female);
    Person MaliaObama= new Person("Malia", "Obama", Sexes.Female);
    Person SashaObama= new Person("Sasha", "Obama", Sexes.Female);
    Person AnnDunham= new Person("Ann", "Dunham", Sexes.Female);
    Person BarackObamaSr= new Person("Barack", "Obama", Sexes.Male);
    BarackObama.setParent(AnnDunham);
    BarackObama.setParent(BarackObamaSr);
    MaliaObama.setParent(BarackObama);
    MaliaObama.setParent(MichelleObama);
    SashaObama.setParent(BarackObama);
    SashaObama.setParent(MichelleObama);
    MyList<Person> osr = new MyList<Person>();
    MyList<Person> ann = new MyList<Person>();
    MyList<Person> oba = new MyList<Person>();
    MyList<Person> mic = new MyList<Person>();
    MyList<Person> mal = new MyList<Person>();
    MyList<Person> sas = new MyList<Person>();
    osr.setValue(BarackObamaSr);
    ann.setValue(AnnDunham);
    oba.setValue(BarackObama);
    mic.setValue(MichelleObama);
    mal.setValue(MaliaObama);
    sas.setValue(SashaObama);
    osr.setNext(ann);
    ann.setNext(oba);
    oba.setNext(mic);
    mic.setNext(mal);
    mal.setNext(sas);
    System.out.println(osr.toString());
    MyList<Person> women = deleteSex(osr,Sexes.Male);
    System.out.println(women.toString());
}  // end main

}  // end BuildLists