Ich versuche, einen Datenbank-Schnittstelle BSTs zu implementieren. Ich habe eine innere Klasse BTSEntry die einen Knoten mit den Variablen Schlüssel, Wert und links / rechts-Knoten darstellt. Jeder linke Knoten weniger (in alphabetischer Reihenfolge) als seine Eltern, während jeder rechter Knoten größer als seine Mutter ist.
Das erste Problem ist, dass ich weiß nicht, was die „nextNode ()“ ist im Entry innere Klasse sein sollte. Ist es einfach der richtige Knoten? Oder ist es, was ich unten getan?
private BinarySearchTreeEntry getLeftMost() {
BinarySearchTreeEntry n = this;
while (n.left != null) {
n = n.left;
}
return n;
}
public BinarySearchTreeEntry getNext() {
if (right != null) {
return right.getLeftMost();
} else {
BinarySearchTreeEntry n = this;
while (n.parent != null && n == n.parent.right) {
n = n.parent;
}
return n.parent;
}
}
Das zweite Problem ist, dass ich nicht wirklich wissen, wie man den „Int Wert get (Str key)“ Methode zu implementieren. EDIT: Ich habe versucht, die get (key) Methode zu tun. Ist es richtig? Arbeitet für diese Rekursion?
public Integer get(String key) throws NoSuchElementException {
BinarySearchTreeEntry curr = root;
if(curr == null){
return null;
} else if(curr.getKey().equals(key)){
return curr.getValue();
} else if(key.compareTo(curr.getKey()) < 0){
curr = curr.getLeft();
get(key);
} else{
curr = curr.getRight();
get(key);
}
return null;
}
Hier ist, was ich bisher getan haben. Jede Hilfe wäre sehr dankbar! :)
package database;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Stack;
public class BinarySearchTree<K, V> implements Dictionary<String, Integer> {
private class BinarySearchTreeEntry
implements DictionaryEntry<String, Integer>{
private String key;
private Integer value;
private BinarySearchTreeEntry left;
private BinarySearchTreeEntry right;
private BinarySearchTreeEntry parent;
BinarySearchTreeEntry(String key, Integer value,
BinarySearchTreeEntry left,
BinarySearchTreeEntry right) {
this.key = key;
this.value = value;
this.left = left;
this.right = right;
if (left != null) left.parent = this;
if (right != null) right.parent = this;
}
private BinarySearchTreeEntry getLeftMost() {
BinarySearchTreeEntry n = this;
while (n.left != null) {
n = n.left;
}
return n;
}
private BinarySearchTreeEntry getRightMost() {
BinarySearchTreeEntry n = this;
while (n.right != null) {
n = n.right;
}
return n;
}
public BinarySearchTreeEntry getNext() {
if (right != null) {
return right.getLeftMost();
} else {
BinarySearchTreeEntry n = this;
while (n.parent != null && n == n.parent.right) {
n = n.parent;
}
return n.parent;
}
}
public String getKey() {
return key;
}
public Integer getValue() {
return value;
}
public BinarySearchTreeEntry getLeft() {
return left;
}
public BinarySearchTreeEntry getRight() {
return right;
}
}
private class ListIterator
implements Iterator<DictionaryEntry<String, Integer>> {
private BinarySearchTreeEntry current;
Stack<BinarySearchTreeEntry> workList;
public ListIterator(BinarySearchTreeEntry entry){
current = entry;
}
public boolean hasNext() {
return current != null;
}
public BinarySearchTreeEntry next() {
BinarySearchTreeEntry result = null;
current = root;
while(current!=null){
workList.push(current);
current = current.getLeft();
}
if(!workList.isEmpty()){
result = (BinarySearchTreeEntry) workList.pop();
current = result.getRight();
}
return result;
}
public void remove() {
}
}
private BinarySearchTreeEntry root;
private int items;
public BinarySearchTree(){
root = null;
items = 0;
}
public int size() {
ListIterator iter = iterator();
while(iter.hasNext()){
items += 1;
}
return items;
}
public boolean isEmpty() {
return size() == 0;
}
public Integer get(String key) throws NoSuchElementException {
BinarySearchTreeEntry curr = root;
if(curr == null){
return null;
} else if(curr.getKey().equals(key)){
return curr.getValue();
} else if(key.compareTo(curr.getKey()) < 0){
//Now what?
}
return null;
}
public void put(String key, Integer value) {
}
public void clear() {
ListIterator iter = iterator();
BinarySearchTreeEntry curr;
curr = root;
while(iter.hasNext()){
remove(curr.getKey());
curr = iter.next();
}
remove(curr.getKey());
}
public void remove(String key) throws NoSuchElementException {
}
public ListIterator iterator() {
return (new ListIterator(root));
}
}
