B_Tree_Operations.cpp

// C++ implementation of search() and traverse() methods
#include<iostream>
using namespace std;
 
// A BTree node
class BTreeNode
{
    int *keys;  // An array of keys
    int t;      // Minimum degree (defines the range for number of keys)
    BTreeNode **C; // An array of child pointers
    int n;     // Current number of keys
    bool leaf; // Is true when node is leaf. Otherwise false
public:
    BTreeNode(int _t, bool _leaf);   // Constructor
 
    // A function to traverse all nodes in a subtree rooted with this node
    void traverse();
 
    // A function to search a key in the subtree rooted with this node.   
    BTreeNode *search(int k);   // returns NULL if k is not present.
 
// Make the BTree friend of this so that we can access private members of this
// class in BTree functions
friend class BTree;
};
 
// A BTree
class BTree
{
    BTreeNode *root; // Pointer to root node
    int t;  // Minimum degree
public:
    // Constructor (Initializes tree as empty)
    BTree(int _t)
    {  root = NULL;  t = _t; }
 
    // function to traverse the tree
    void traverse()
    {  if (root != NULL) root->traverse(); }
 
    // function to search a key in this tree
    BTreeNode* search(int k)
    {  return (root == NULL)? NULL : root->search(k); }
};
 
// Constructor for BTreeNode class
BTreeNode::BTreeNode(int _t, bool _leaf)
{
    // Copy the given minimum degree and leaf property
    t = _t;
    leaf = _leaf;
 
    // Allocate memory for maximum number of possible keys
    // and child pointers
    keys = new int[2*t-1];
    C = new BTreeNode *[2*t];
 
    // Initialize the number of keys as 0
    n = 0;
}
 
// Function to traverse all nodes in a subtree rooted with this node
void BTreeNode::traverse()
{
    // There are n keys and n+1 children, traverse through n keys
    // and first n children
    int i;
    for (i = 0; i < n; i++)
    {
        // If this is not leaf, then before printing key[i],
        // traverse the subtree rooted with child C[i].
        if (leaf == false)
            C[i]->traverse();
        cout << " " << keys[i];
    }
 
    // Print the subtree rooted with last child
    if (leaf == false)
        C[i]->traverse();
}
 
// Function to search key k in subtree rooted with this node
BTreeNode *BTreeNode::search(int k)
{
    // Find the first key greater than or equal to k
    int i = 0;
    while (i < n && k > keys[i])
        i++;
 
    // If the found key is equal to k, return this node
    if (keys[i] == k)
        return this;
 
    // If the key is not found here and this is a leaf node
    if (leaf == true)
        return NULL;
 
    // Go to the appropriate child
    return C[i]->search(k);
}