Java B+;树裂蝽
我想站在前面,所以我会说我将要谈论的家庭作业。我们假设做一个B+树。大多数情况下我都有,但是当我有一个节点分裂时,我遇到了一个问题。特别是当节点是非叶节点(不包括根节点)并且它分裂时,我将丢失最右指针 例如,如果树是Java B+;树裂蝽,java,b-tree,Java,B Tree,我想站在前面,所以我会说我将要谈论的家庭作业。我们假设做一个B+树。大多数情况下我都有,但是当我有一个节点分裂时,我遇到了一个问题。特别是当节点是非叶节点(不包括根节点)并且它分裂时,我将丢失最右指针 例如,如果树是 |3 5| |1 2| |4| |5 6| 我丢失了指向| 5 6 |的指针。因此,当我搜索这些值时,我找不到它们,或者当我添加一个遵循该路径的值时,我会得到一个空
|3 5|
|1 2| |4| |5 6|
我丢失了指向| 5 6 |
的指针。因此,当我搜索这些值时,我找不到它们,或者当我添加一个遵循该路径的值时,我会得到一个空指针异常
不管怎样,我通常只会把我的代码粘贴在这里,但不幸的是,我们学校出现了作弊问题,由于该项目即将到期,我相信我的很多同学都在互联网上搜寻代码。我最不想发生的事就是某个混蛋盗取我的代码
如果有人不介意看一下代码,我会很乐意把它发给你,让你看看。同样,它是用Java编写的,而且相当长
提前谢谢
这是代码。在侧节点上,当我清除偏移和关键点时,我使用int和long MAX_值,因此当我排序时,我知道这些清除的值将转到节点的末尾。拆分类只是一个愚蠢的想法,我需要修复之前的问题。它由节点、偏移和关键点组成。最初我认为可能需要返回一个不在分割节点中的偏移量和关键点。然后我意识到这很愚蠢,我需要返回的只是新节点本身
public void add (int key, long offset) throws IOException
{
if (root != null) //start search of where to add the book
{
SplitBucket split = add(root, key, offset); //recursive call
if (split != null) //root has split
{
long newRootOffset;
//make new root and have it point to old root and the split node
BookNode newRoot = new BookNode();
newRoot.changeCurrentChildren(1);
newRoot.setChildKey(0, split.key);
newRoot.setChildOffset(0, root.getMyOffset());
newRoot.setChildOffset(1, split.offset);
newRoot.setChildOffset(2,
root.getChildOffset(Constants.childSize -1));
newRoot.setNode(0, root);
newRoot.setNode(1, split.node);
newRoot.setNode(2, root.getNode(Constants.childSize - 1));
io.setBookNode(root.getMyOffset(), root);
newRootOffset = io.insertNewNode(newRoot);
io.setRoot(newRootOffset);
root = newRoot;
}
}
else //empty tree so create root and add
{
long rootOffset = Long.MAX_VALUE;
root = new BookNode();
root.setChildKey(0, key);
root.setChildOffset(0, offset);
root.changeCurrentChildren(1);
root.switchLeaf(true);
rootOffset = io.insertNewNode(root);
io.setRoot(rootOffset);
root.setMyOffset(rootOffset);
}
}
/**
*
* @param current current BookNode
* @param key Isbn to add
* @param offset offset of Book to add
* @return BookNode if a split occurs
* @throws IOException
*/
private SplitBucket add (BookNode current, int key, long offset)
throws IOException
{
if (current.isLeaf()) // at the bottom level
{
//room to add
if (current.getCurrentChildren() < Constants.childSize - 1)
{
//add the offset and key to the end of the node.
//sort the node and rewrite to file
current.setChildOffset(current.getCurrentChildren(), offset);
current.setChildKey(current.getCurrentChildren(), key);
current.changeCurrentChildren(1);
current.sortKeysAndOffsets();
io.setBookNode(current.getMyOffset(), current);
return null;
}
else //not enough room must split
{ //add offset and key to end of node and sort
current.setChildKey(current.getCurrentChildren(), key);
current.setChildOffset(current.getCurrentChildren(), offset);
current.changeCurrentChildren(1);
current.sortKeysAndOffsets();
int start = current.getCurrentChildren() / 2;
long newNodeOffset =Long.MAX_VALUE;
SplitBucket bucket = new SplitBucket();
BookNode newNode = new BookNode();
newNode.switchLeaf(true);
for(int i = start; i < Constants.childSize; i++)
{
//new node will hold the larger split values
newNode.setChildKey(i - start, current.getChildKey(i));
newNode.setChildOffset(i - start, current.getChildOffset(i));
newNode.setNode(i - start, current.getNode(i));
newNode.changeCurrentChildren(1);
current.setChildKey(i, Integer.MAX_VALUE);
current.setChildOffset(i, Long.MAX_VALUE);
current.setNode(i, null);
current.changeCurrentChildren(-1);
}
//since sorted prior to for loop all data
//needs not to be sorted again
newNode.sortKeysAndOffsets();
current.sortKeysAndOffsets();
//Transferring pre-split nodes 'next' pointer to new node
newNode.setChildOffset(Constants.childSize,
current.getChildOffset(Constants.childSize));
newNode.setNode(Constants.childSize,
current.getNode(Constants.childSize));
newNodeOffset = io.insertNewNode(newNode);
newNode.setMyOffset(newNodeOffset);
current.setChildOffset(Constants.childSize, newNodeOffset);
current.setNode(Constants.childSize, newNode);
io.setBookNode(current.getMyOffset(), current);
bucket.key = newNode.getChildKey(0);
bucket.offset = newNode.getMyOffset();
bucket.node = newNode;
return bucket;
}
}
else //not at a leaf
{
int index = 0;
//find pointer index to follow
while (index < current.getCurrentChildren()
&& key >= current.getChildKey(index))
{
index++;
}
//recursive call
SplitBucket bucket = add(current.getNode(index), key, offset);
if(bucket != null) //split occurred
{
//bucket not full so add here
if(current.getCurrentChildren() < Constants.childSize)
{
current.setChildKey(current.getCurrentChildren(), bucket.key);
current.setChildOffset(current.getCurrentChildren(),
bucket.offset);
current.setNode(current.getCurrentChildren(), bucket.node);
current.changeCurrentChildren(1);
current.sortKeysAndOffsets();
io.setBookNode(current.getMyOffset(), current);
bucket = null;
}
else //bucket is full so split
{
int start = current.getCurrentChildren() / 2;
long newNodeOffset = Long.MAX_VALUE;
BookNode newNode = new BookNode();
for(int i = start; i < Constants.childSize; i++)
{
//larger keys go to the new node
newNode.setChildKey(i - start, current.getChildKey(i));
newNode.setChildOffset(i - start,
current.getChildOffset(i));
newNode.setNode(i - start, current.getNode(i));
newNode.changeCurrentChildren(1);
current.setChildKey(i, Integer.MAX_VALUE);
current.setChildOffset(i, Long.MAX_VALUE);
current.setNode(i, null);
current.changeCurrentChildren(-1);
}
if(bucket.key > newNode.getChildKey(0)) //goes in new bucket
{
newNode.setChildKey(newNode.getCurrentChildren(),
bucket.key);
newNode.setChildOffset(newNode.getCurrentChildren(),
bucket.offset);
newNode.setNode(newNode.getCurrentChildren(),
bucket.node);
newNode.changeCurrentChildren(1);
newNode.sortKeysAndOffsets();
}
else //goes in old bucket
{
current.setChildKey(current.getCurrentChildren(),
bucket.key);
current.setChildOffset(current.getCurrentChildren(),
bucket.offset);
current.setNode(current.getCurrentChildren(),
bucket.node);
current.changeCurrentChildren(1);
current.sortKeysAndOffsets();
}
//may not need this line and next
newNode.setChildOffset(newNode.getCurrentChildren(),
current.getChildOffset(Constants.childSize));
newNode.setNode(newNode.getCurrentChildren(),
current.getNode(Constants.childSize));
newNodeOffset = io.insertNewNode(newNode);
newNode.setMyOffset(newNodeOffset);
io.setBookNode(current.getMyOffset(), current);
bucket = new SplitBucket();
//return middle key value of split node
bucket.key = newNode.getChildKey(
newNode.getCurrentChildren() /2);
bucket.offset = newNode.getMyOffset();
bucket.node = newNode;
return bucket;
}
}
}
return null;
}
public void add(int键,长偏移量)引发IOException
{
if(root!=null)//开始搜索添加书籍的位置
{
SplitBucket split=add(根、键、偏移量);//递归调用
if(split!=null)//根目录已拆分
{
长新根偏移量;
//创建新根并使其指向旧根和拆分节点
BookNode newRoot=新BookNode();
newRoot.changeCurrentChildren(1);
newRoot.setChildKey(0,split.key);
setChildOffset(0,root.getMyOffset());
newRoot.setChildOffset(1,split.offset);
newRoot.setChildOffset(2,
getChildOffset(Constants.childSize-1);
setNode(0,根);
setNode(1,split.node);
setNode(2,root.getNode(Constants.childSize-1));
io.setBookNode(root.getMyOffset(),root);
newRootOffset=io.insertNewNode(newRoot);
io.setRoot(newRootOffset);
根=新根;
}
}
else//清空树,以便创建根并添加
{
long rootOffset=long.MAX_值;
root=newbooknode();
root.setChildKey(0,key);
root.setChildOffset(0,偏移量);
root.changeCurrentChildren(1);
根。开关叶(真);
rootOffset=io.insertNewNode(根);
io.setRoot(rootOffset);
根.setMyOffset(rootOffset);
}
}
/**
*
*@param current BookNode
*@param key要添加的Isbn
*@param要添加的书本偏移量
*@发生拆分时返回BookNode
*@抛出异常
*/
专用SplitBucket添加(BookNode当前、int键、长偏移量)
抛出IOException
{
if(current.isLeaf())//位于底层
{
//添加空间
if(current.getCurrentChildren()