Java - 再帰的リンクリストの実装

Question

私は完全に単独のリンクリスト（以下のコード）を実装していますが、割り当ては再帰を使用して実装するよう具体的に要求しています。私は再帰呼び出しに書いたwhileループを翻訳しようとしていましたが、スタックしていくつかの助けを得ることができました。再帰での最近の試みはコードに含まれていますが、コメントアウトされています。事前に助けていただきありがとうございます。

public class AddressList 
{ 
public Record firstLink ; 
public String name, tel, email, addr, state, dob; 
AddressList() 
{ 
    firstLink = null; 
} 

public boolean isEmpty() 
{ 
    return(firstLink == null); 
} 

public void addToFront(Record record) 
{ 
    if(firstLink == null) 
    { 
     firstLink = new Record(record.getName(), record.getTel(), record.getEmail(), record.getAddr(), 
      record.getState(), record.getDob()); 
    } 
    else 
    { 
     Record newRecord = new Record(record.getName(), record.getTel(), record.getEmail(), record.getAddr(), 
       record.getState(), record.getDob()); 
     newRecord.setNext(firstLink); 
     firstLink = newRecord; 
    } 
} 

public void addToBack(Record record) 
{ 
    if(firstLink == null) 
    { 
     firstLink = new Record(record.getName(), record.getTel(), record.getEmail(), record.getAddr(), 
      record.getState(), record.getDob()); 
    } 
    else 
    { 
     Record newRecord = new Record(record.getName(), record.getTel(), record.getEmail(), record.getAddr(), 
       record.getState(), record.getDob()); 
     Record currentRecord = firstLink; 
     while(currentRecord.getNext() != null) 
     { 
      currentRecord = currentRecord.getNext(); 
     } 
     currentRecord.setNext(newRecord); 
    } 
    /* 
    if(firstLink == null) 
    { 
    firstLink = new Record(record.getName(), record.getTel(), record.getEmail(), record.getAddr(), 
    record.getState(), record.getDob()); 
    } 
    else if (firstLink.getNext() == null) 
    { 
    firstLink.setNext(new Record(record.getName(), record.getTel(), record.getEmail(), record.getAddr(), 
    record.getState(), record.getDob())); 
    } 
    else 
    { 
    Record newRecord = new Record(record.getName(), record.getTel(), record.getEmail(), record.getAddr(), 
    record.getState(), record.getDob()); 
    newRecord.setNext(firstLink); 
    firstLink = newRecord; 
    addToBack(newRecord); 
    }*/ 

    /* 
    else 
    { 
    add 
    } 
    { 
    Record newRecord = new Record(record.getName(), record.getTel(), record.getEmail(), record.getAddr(), 
    record.getState(), record.getDob()); 
    Record current = firstLink; 
    if(current.getNext() == null) 
    current.setNext(newRecord); 
    else 
    addToBack(current.getNext()); 
    } 
    */ 

} 

public String toString() 
{ 
    if(firstLink == null) 
     return "Empty List\n\n"; 
    String result = ""; 
    Record current = firstLink; 
    result += "\nName: "+current.getName()+"\nTelephone: "+current.getTel()+"\nEmail: "+current.getEmail()+ 
    "\nAddress: "+current.getAddr()+"\nState: "+current.getState()+"\nDOB: "+current.getDob()+"\n\n"; 
    while(current.getNext() != null) 
    { 
     current = current.getNext(); 
     result += "\nName: "+current.getName()+"\nTelephone: "+current.getTel()+"\nEmail: "+current.getEmail()+ 
     "\nAddress: "+current.getAddr()+"\nState: "+current.getState()+"\nDOB: "+current.getDob()+"\n\n"; 
    } 
    return "List: \n\n"+result; 
} 

public void reverse() 
{ 
    Record previousRecord = null; 
    Record currentRecord = firstLink; 
    while (currentRecord != null) 
    { 
     Record nextRecord = currentRecord.getNext(); 
     currentRecord.setNext(previousRecord); 
     previousRecord = currentRecord; 
     currentRecord = nextRecord; 
    } 
    firstLink = previousRecord; 
} 

public int sizeOf() 
{ 
    Record currentRecord = firstLink; 
    int size = 1; 
    if (currentRecord == null) 
    { 
     return 0; 
    } 
    else 
    { 
     while (currentRecord.getNext() != null) 
     { 
      size++; 
      currentRecord = currentRecord.getNext(); 
     } 
    } 
    return size; 
} 

public String phoneNumberByName(String name) 
{ 
    Record currentRecord = firstLink; 
    while(currentRecord.getName().equals(name) == false) 
    { 
     currentRecord = currentRecord.getNext(); 
    } 
    return currentRecord.getTel(); 
    /* 
    Record currentRecord = firstLink; 
    if (currentRecord.getName().equals(name)) 
    { 
    return currentRecord.getTel(); 
    } 
    else 
    { 
    firstLink = currentRecord.getNext(); 
    phoneNumberByName(name); 

    } 
    return "Unexpected behaviour. You should never see this message."; 
    */ 

} 

public String emailByName(String name) 
{ 
    Record currentRecord = firstLink; 
    while(currentRecord.getName().equals(name) == false) 
    { 
     currentRecord = currentRecord.getNext(); 
    } 
    return currentRecord.getEmail(); 
} 

public String nameByPhoneNumber(String tel) 
{ 
    Record currentRecord = firstLink; 
    while(currentRecord.getTel().equals(tel) == false) 
    { 
     currentRecord = currentRecord.getNext(); 
    } 
    return currentRecord.getName(); 
} 

public String dobByName(String name) 
{ 
    Record currentRecord = firstLink; 
    while (currentRecord.getName().equals(name) == false) 
    { 
     currentRecord = currentRecord.getNext(); 
    } 
    return currentRecord.getDob(); 
} 

}

Recordクラス、場合にあなたもいることが必要です。

public class Record 
{ 
private String name; 
private String tel; // Telephone number 
private String email; 
private String addr; // Address 
private String dob; // Date of birth 
private String state; 
private Record next = null; 

public Record(String name, String tel, String email, String addr, String state, String dob) 
{ 
    this.name = name; 
    this.tel = tel; 
    this.email = email; 
    this.addr = addr; 
    this.dob = dob; 
    this.state = state; 
    //this.next = null; 
} // end of the constructor 

public String getName() 
{ return name; } 

public String getTel() 
{ return tel; } 

public String getEmail() 
{ return email; } 

public String getAddr() 
{ return addr; } 

public String getState() 
{ return state; } 

public String getDob() 
{return dob; } 

public void setName(String name) 
{ this.name = name; } 

public void setTel(String tel) 
{ this.tel = tel; } 

public void setEmail(String email) 
{ this.email = email; } 

public void setAddr(String addr) 
{ this.addr = addr; } 

public void setState(String state) 
{ this.state = state; } 

public void setDob(String dob) 
{ this.dob = dob; } 

public Record getNext() 
{ return next; } 

public void setNext(Record record) 
{ next = record; } 

}

Answer 1

再帰addToBackはかなり単純です。既存の非再帰的である擬似コードでは、：

：より良い実装は、より再利用可能な findLast内部方法であるかもしれない

public void addToBack(rec) { 
    if (first == null) 
     first = new(rec) 
    else 
     addToBackInternal(first, rec) 
} 

private void addToBackInternal(curr, rec) { 
    if (curr.next == null) 
     curr.next = new(rec) 
    else 
     addToBackInternal(curr.next, rec) 
} 

：

再帰として

public void addToBack(rec) { 
    if (first == null) 
     first = new(rec) 
    else { 
     curr = first; 
     while (curr.next != null) 
      curr = curr.next 
     curr.next = new(rec) 
    } 
} 

、それは二つの方法でなければならないであろう

public void addToBack(rec) { 
    if (first == null) 
     first = new(rec) 
    else 
     findLast(first).next = new(rec) 
} 

private Node findLast(curr) { 
    if (curr.next == null) 
     return curr 
    return findLast(curr.next) 
}