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我有一個問題，添加值會在我的234樹超出第一級創建一個新的水平。我的方法在根對象上創建子對象，但無法爲其他任何節點創建子對象。我能夠創建並插入給定數量的數據對象，只要它們不填充節點，從而創建一個子節點......我已經認真地梳理了好幾天。234樹插入方法問題
我的問題基本上是基於我的代碼。我的方法（特別是插入方法）是否允許在根下創建子節點？
樹類
public class Tree234 {
public Node root = new Node(); // make root node
public int find(String key) {
Node focus = root;
int childNumber;
while (true) {
if ((childNumber = focus.findItem(key)) != -1) {
return childNumber; // found it
} else if (focus.isLeaf()) {
return -1; // can't find it
} else // search deeper
{
focus = getNextChild(focus, key);
}
} // end while
}
// insert a DataItem
public void insert(String dWord) { // Performs the splits
// in a top-down (root -----> leaf) fashion.
Node focus = root;
DataItem tempItem = new DataItem(dWord);
while (true) {
if (focus.isFull()) { // if node full
System.out.println("Need to split!");
split(focus); // split it
System.out.println("Splint done?");
focus = focus.getParent(); // back up
// search once
focus = getNextChild(focus, dWord);
} // end if (node is full)
else if (focus.isLeaf()) { // if node is leaf
break; // jump to insert
} else { // node is not full, not a leaf; so go to lower level
focus = getNextChild(focus, dWord);
}
} // end while
// insert new DataItem
focus.insertItem(tempItem);
} // end insert
public void split(Node thisNode) { // split the node
// assumes node is full
DataItem itemB, itemC;
Node parent, child2, child3;
int itemIndex;
// two right most items are removed from the node and stored
itemC = thisNode.removeItem(); // remove items from
itemB = thisNode.removeItem(); // this node
child2 = thisNode.disconnectChild(2); // remove children
child3 = thisNode.disconnectChild(3); // from this node
// make new node, goes to the right of the node being split
Node newRight = new Node();
if (thisNode == root) { // if this is the root
// make new root
root = new Node();
// root is our parent
parent = root;
// connect to parent
root.connectChild(0, thisNode);
} else {// this node not the root get parent
parent = thisNode.getParent();
}
// deal with parent
// item B is inserted in the parent node
itemIndex = parent.insertItem(itemB); // deal with parent
// total items?
int n = parent.getNumItems();
// move parent's connections
// one child to the right
for (int j = n - 1; j < itemIndex; j--) {
Node temp = parent.disconnectChild(j);
parent.connectChild(j + 1, temp);
}
// connect newRight to parent
parent.connectChild(itemIndex + 1, newRight);
// deal with newRight
newRight.insertItem(itemC); // item C to newRight
newRight.connectChild(0, child2); // connect to 0 and 1
newRight.connectChild(1, child3); // on newRight
} // end split()
public Node getNextChild(Node theNode, String keyWord) {
int j;
// assumes node is not empty, not full, not a leaf
int numItems = theNode.getNumItems();
// for each item in node
for (j = 0; j < numItems; j++) {
// is the value given less than the value at the
//first index of the array?
if (keyWord.compareToIgnoreCase(theNode.getItem(j).dData) < 0) {
// if so, return left child so we can use it at another
// point in time
return theNode.getChild(j);
}
} // end for
return theNode.getChild(j);
// otherwise, our value is greater we're greater, so
// we return right child (the child right after the
// value given, greater)
}
public void displayTree() {
recDisplayTree(root, 0, 0);
}
public void recDisplayTree(Node thisNode, int level, int childNumber) {
System.out.print("level=" + level + " child=" + childNumber + " ");
thisNode.displayNode(); // display this node
// call ourselves for each child of this node
int numItems = thisNode.getNumItems();
for (int j = 0; j < numItems + 1; j++) {
Node nextNode = thisNode.getChild(j);
if (nextNode != null) {
recDisplayTree(nextNode, level + 1, j);
} else {
return;
}
}
} // end recDisplayTree()
}
通常我只會張貼我詢問具體的代碼。然而這個特定的方法也跳入了其他兩個類。所以我認爲看到我如何讓他們成立會有一些好處。
節點類
public class Node {
// Max size
private static final int SIZE = 4;
public int numItems;
public Node parent;
public Node children[] = new Node[SIZE];
public DataItem items[] = new DataItem[SIZE - 1];
public void connectChild(int childNum, Node child) { // Connect child to this Node
children[childNum] = child;
if (child != null) {
child.parent = this;
}
}
public Node disconnectChild(int childNum) { // Disconnect child from this Node
Node temp = children[childNum];
children[childNum] = null;
return temp;
}
public Node getChild(int childNum) { // Returns child
return children[childNum];
}
public Node getParent() { // Returns parent
return parent;
}
public Boolean isLeaf() {
// test if child is a leaf
return children[0] == null;
}
public int getNumItems() {
return numItems;
}
public DataItem getItem(int index) {
return items[index];
}
public Boolean isFull() {
return numItems == SIZE - 1;
}
public int findItem(String term) {
for (int j = 0; j < SIZE; j++) {
if (items[j] == null) {
break;
} else if (items[j].dData.equalsIgnoreCase(term)) {
return j;
}
}
return -1;
} // end findItem()
public int insertItem(DataItem newItem) {
if (findItem(newItem.dData) != -1) {
items[findItem(newItem.dData)].count++;
return 0;
}
numItems++; // will add new item
String newKey = newItem.dData;
for (int j = numItems-1; j >= 0; j--) {
if (items[j] != null){
System.out.println(items[j].dData);
}
if (items[j] == null) {
continue;
} else {
String itsKey = items[j].dData;
if (newKey.compareToIgnoreCase(itsKey) < 0) {
items[j + 1] = items[j];
} else {
items[j + 1] = newItem;
return j + 1;
}
} // end else (not null)
} // end for ----> // shifted all items,
items[0] = newItem; // insert new item
return 0;
} // end insertItem()
public DataItem removeItem() {
DataItem temp = items[numItems - 1];
items[numItems - 1] = null;
numItems--;
return temp;
}
public void displayNode() {
for (int j = 0; j < numItems; j++) {
items[j].displayItem();
}
System.out.println();
}
} // end class Node
我把一切都設置爲公共現在的我只是測試代碼的結構。
的DataItem的類
public class DataItem {
public String dData;
public int count;
public DataItem(String term) {
dData = term;
count = 1;
}
public String getItem() {
return this.dData;
}
public int getCount() {
return this.count;
}
public void displayItem() {
System.out.print("\nWord: " + dData + "\t\tCount: " + count);
}
}
這是我如何我添加的DataItem對象樹。
public class Main {
public static void main(String[] args) {
Tree234 tree = new Tree234();
for (int i = 0; i < 13; i++) {
String temp = RandomName.getLast();
System.out.println(temp);
tree.insert(temp);
}
tree.displayTree();
}
輸出
Townsend
George
Townsend
Welch
Townsend
Clemons
George
Rose
George
Bond
Townsend
Clemons
Bowers
Clemons
Bond
Foreman
Townsend
George
Clemons
Hahn
Townsend
Alston
Bond
Petersen
Townsend
Hahn
Hansen
George
Hahn
Moses
Hansen
level=0 child=0
Word: George Count: 1
Word: Petersen Count: 1
level=1 child=0
Word: Bowers Count: 1
level=2 child=0
Word: Alston Count: 1
Word: Bond Count: 1
level=2 child=1
Word: Clemons Count: 1
Word: Foreman Count: 1
level=1 child=1
Word: Hahn Count: 1
Word: Hansen Count: 1
Word: Moses Count: 1
level=1 child=2
Word: Townsend Count: 1
樹 「似乎」 的工作，但增加超過10名開始使它不穩定。根本無法處理15個或更多。
有15個或更多Bowman
Moore
Bowman
Anthony
Moore
Bowman
Graham
Moore
Nielsen
Exception in thread "main" java.lang.NullPointerException
Moore
Camacho
Bowman
Graham
Herman
Graham
Gallagher
Moore
Bowman
Camacho
Hartman
Herman
Daniels
Gallagher
Camacho
Snyder
at dataPackage.Tree234.insert(Tree234.java:40)
at testPackage.Main.main(Main.java:31)
X:\source\234Tree\234Tree\nbproject\build-impl.xml:1040: The following error occurred while executing this line:
X:\source\234Tree\234Tree\nbproject\build-impl.xml:805: Java returned: 1
BUILD FAILED (total time: 0 seconds)
輸出我仍然相當新的算法，這樣我可以完全是簡單的東西。我開始認爲插入方法很好，但我可能不會正確分割。這就是爲什麼我現在可以插入到2級而不是更遠。感謝您的任何見解。