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BTree.java
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//-----------------------------------------------------------------------
//this will be the BTree class which all methods being performed on tree|
//are located. This will call methods in BNode.java and the methods in |
//this class will be used to do operations on a tree object. | |
//-----------------------------------------------------------------------
//This is class project for CS380 Data Structures and Algorithm Analysis|
//the basic format of this program is derived from class notes and |
//psuedocode in Intoduction to Algorithms, 2nd Edition, Cormen et.al. |
//MIT Press, Cambridge. |
//Jeremy Phelps and Kris |
//-----------------------------------------------------------------------
public class BTree
{
// here are variables available to tree
static int order; // order of tree
BNode root; //every tree has at least a root node
// ---------------------------------------------------------
// here is the constructor for tree |
// ---------------------------------------------------------
public BTree(int order)
{
this.order = order;
root = new BNode(order, null);
}
// --------------------------------------------------------
// this will be method to search for a given node where |
// we want to insert a key value. this method is called |
// from SearchnPrintNode. It returns a node with key |
// value in it |
// --------------------------------------------------------
public BNode search(BNode root, int key)
{
int i = 0;//we always want to start searching the 0th index of node.
while(i < root.count && key > root.key[i])//keep incrementing
//in node while key >
//current value.
{
i++;
}
if(i <= root.count && key == root.key[i])//obviously if key is in node
//we went to return node.
{
return root;
}
if(root.leaf)//since we've already checked root
//if it is leaf we don't have anything else to check
{
return null ;
}
else//else if it is not leave recurse down through ith child
{
return search(root.getChild(i),key);
}
}
// --------------------------------------------------------
// this will be the split method. It will split node we |
// want to insert into if it is full. |
// --------------------------------------------------------
public void split(BNode x, int i, BNode y)
{
BNode z = new BNode(order,null);//gotta have extra node if we are
//to split.
z.leaf = y.leaf;//set boolean to same as y
z.count = order - 1;//this is updated size
for(int j = 0; j < order - 1; j++)
{
z.key[j] = y.key[j+order]; //copy end of y into front of z
}
if(!y.leaf)//if not leaf we have to reassign child nodes.
{
for(int k = 0; k < order; k++)
{
z.child[k] = y.child[k+order]; //reassing child of y
}
}
y.count = order - 1; //new size of y
for(int j = x.count ; j> i ; j--)//if we push key into x we have
{ //to rearrange child nodes
x.child[j+1] = x.child[j]; //shift children of x
}
x.child[i+1] = z; //reassign i+1 child of x
for(int j = x.count; j> i; j--)
{
x.key[j + 1] = x.key[j]; // shift keys
}
x.key[i] = y.key[order-1];//finally push value up into root.
y.key[order-1 ] = 0; //erase value where we pushed from
for(int j = 0; j < order - 1; j++)
{
y.key[j + order] = 0; //'delete' old values
}
x.count ++; //increase count of keys in x
}
// ----------------------------------------------------------
// this will be insert method when node is not full. |
// ----------------------------------------------------------
public void nonfullInsert(BNode x, int key)
{
int i = x.count; //i is number of keys in node x
if(x.leaf)
{
while(i >= 1 && key < x.key[i-1])//here find spot to put key.
{
x.key[i] = x.key[i-1];//shift values to make room
i--;//decrement
}
x.key[i] = key;//finally assign value to node
x.count ++; //increment count of keys in this node now.
}
else
{
int j = 0;
while(j < x.count && key > x.key[j])//find spot to recurse
{ //on correct child
j++;
}
// i++;
if(x.child[j].count == order*2 - 1)
{
split(x,j,x.child[j]);//call split on node x's ith child
if(key > x.key[j])
{
j++;
}
}
nonfullInsert(x.child[j],key);//recurse
}
}
//--------------------------------------------------------------
//this will be the method to insert in general, it will call |
//insert non full if needed. |
//--------------------------------------------------------------
public void insert(BTree t, int key)
{
BNode r = t.root;//this method finds the node to be inserted as
//it goes through this starting at root node.
if(r.count == 2*order - 1)//if is full
{
BNode s = new BNode(order,null);//new node
t.root = s; //\
// \
s.leaf = false;// \
// > this is to initialize node.
s.count = 0; // /
// /
s.child[0] = r;///
split(s,0,r);//split root
nonfullInsert(s, key); //call insert method
}
else
nonfullInsert(r,key);//if its not full just insert it
}
// ---------------------------------------------------------------------------------
// this will be method to print out a node, or recurses when root node is not leaf |
// ---------------------------------------------------------------------------------
public void print(BNode n)
{
for(int i = 0; i < n.count; i++)
{
System.out.print(n.getValue(i)+" " );//this part prints root node
}
if(!n.leaf)//this is called when root is not leaf;
{
for(int j = 0; j <= n.count ; j++)//in this loop we recurse
{ //to print out tree in
if(n.getChild(j) != null) //preorder fashion.
{ //going from left most
System.out.println(); //child to right most
print(n.getChild(j)); //child.
}
}
}
}
// ------------------------------------------------------------
// this will be method to print out a node |
// ------------------------------------------------------------
public void SearchPrintNode( BTree T,int x)
{
BNode temp= new BNode(order,null);
temp= search(T.root,x);
if (temp==null)
{
System.out.println("The Key does not exist in this tree");
}
else
{
print(temp);
}
}
//--------------------------------------------------------------
//this method will delete a key value from the leaf node it is |
//in. We will use the search method to traverse through the |
//tree to find the node where the key is in. We will then |
//iterated through key[] array until we get to node and will |
//assign k[i] = k[i+1] overwriting key we want to delete and |
//keeping blank spots out as well. Note that this is the most |
//simple case of delete that there is and we will not have time|
//to implement all cases properly. |
//--------------------------------------------------------------
public void deleteKey(BTree t, int key)
{
BNode temp = new BNode(order,null);//temp Bnode
temp = search(t.root,key);//call of search method on tree for key
if(temp.leaf && temp.count > order - 1)
{
int i = 0;
while( key > temp.getValue(i))
{
i++;
}
for(int j = i; j < 2*order - 2; j++)
{
temp.key[j] = temp.getValue(j+1);
}
temp.count --;
}
else
{
System.out.println("This node is either not a leaf or has less than order - 1 keys.");
}
}
}