2-3 Tree: How do i search for a node? - c++

Question

This is my code so far:
Its a 2-3 tree implementation
#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
// TwoThreeNode class
class TwoThreeNode {
private:
// Gets the value of the smallest data item in the subtree
// rooted by this node
int getSmallest() {
TwoThreeNode *node = this;
while (!node->isLeaf()) node = node->child[0];
return node->key[0];
}
// Insert into a node with 1 child
void insert1Siblings(TwoThreeNode *newChild, int newSmallest) {
int newKey = newChild->key[0];
newChild->parent = this;
if (newKey < child[0]->key[0]) {
// newNode is inserted as first child of root
child[1] = child[0];
child[0] = newChild;
key[0] = child[1]->getSmallest();
}
else {
// newNode is iserted as second child of root
child[1] = newChild;
key[0] = newSmallest;
}
}
// Insert into a node with 2 children
void insert2Siblings(TwoThreeNode *newChild, int newSmallest) {
int newKey = newChild->key[0];
newChild->parent = this;
if (newKey < child[0]->key[0]) {
child[2] = child[1];
child[1] = child[0];
child[0] = newChild;
key[1] = key[0];
key[0] = child[1]->getSmallest();
updateParentSmallest(newSmallest);
}
else if (newKey < child[1]->key[0]) {
child[2] = child[1];
child[1] = newChild;
key[1] = key[0];
key[0] = newSmallest;
}
else {
child[2] = newChild;
key[1] = newSmallest;
}
}
// Insert into a node with 3 children
void insert3Siblings(TwoThreeNode *newChild, int newSmallest) {
int newKey = newChild->key[0];
int splitSmallest = -1;
TwoThreeNode *splitNode = new TwoThreeNode();
splitNode->parent = parent;
if (newKey < child[0]->key[0] || newKey < child[1]->key[0]) {
// newChild is inserted in current node
splitSmallest = key[0];
splitNode->child[0] = child[1];
splitNode->child[1] = child[2];
splitNode->key[0] = key[1];
child[1]->parent = splitNode;
child[2]->parent = splitNode;
newChild->parent = this;
if (newKey < child[0]->key[0]) {
// newChild is inserted as first child
child[1] = child[0];
child[0] = newChild;
key[0] = child[1]->getSmallest();
updateParentSmallest(newSmallest);
}
else {
// newChild is inserted as second child
child[1] = newChild;
key[0] = newSmallest;
}
}
else {
// newChild is inserted in split node
child[2]->parent = splitNode;
newChild->parent = splitNode;
if (newKey < child[2]->key[0]) {
// newChild is inserted as first child
splitSmallest = newSmallest;
splitNode->child[0] = newChild;
splitNode->child[1] = child[2];
splitNode->key[0] = key[1];
}
else {
// newChild is inserted as second child
splitSmallest = key[1];
splitNode->child[0] = child[2];
splitNode->child[1] = newChild;
splitNode->key[0] = newSmallest;
}
}
child[2] = NULL;
key[1] = -1;
if (parent->parent == NULL) {
// At root, so new root needs to be created
TwoThreeNode *newNode = new TwoThreeNode();
parent->child[0] = newNode;
newNode->parent = parent;
newNode->child[0] = this;
parent = newNode;
}
parent->insert(splitNode, splitSmallest);
}
// Update the parent nods efor the smallest child value
void updateParentSmallest(int data) {
switch (sibNumber()) {
case 0: if (parent->parent != NULL) parent->updateParentSmallest(data); break;
case 1: parent->key[0] = data; break;
case 2: parent->key[1] = data; break;
}
}
public:
int key[2];
TwoThreeNode *parent, *child[3];
// Constructor
TwoThreeNode(int data = -1) {
key[0] = data;
key[1] = -1;
parent = child[0] = child[1] = child[2] = NULL;
}
// Check if node is a leaf
bool isLeaf() {
return (child[0] == NULL);
}
// Get which sibling the node is
int sibNumber() {
for (int i = 0; i < 3; ++i) {
if (this == parent->child[i]) return i;
}
return -1;
}
// Insertion
void insert(TwoThreeNode *newChild, int newSmallest) {
if (child[1] == NULL) insert1Siblings(newChild, newSmallest);
else if (child[2] == NULL) insert2Siblings(newChild, newSmallest);
else insert3Siblings(newChild, newSmallest);
}
};
// TwoThreeTree class
class TwoThreeTree {
private:
TwoThreeNode *root;
// Find the appropriate operation point
TwoThreeNode* findSpot(TwoThreeNode *node, int data) {
if (node == NULL) return NULL;
while (!node->isLeaf()) {
if (node->key[0] == data || node->key[1] == data)
return NULL;
if (node->key[0] == -1 || data < node->key[0])
node = node->child[0];
else if (node->key[1] == -1 || data < node->key[1])
node = node->child[1];
else
node = node->child[2];
}
if (node->key[0] == data) return NULL;
return node->parent;
}
// Recursively print the subtree starting from the given node
void print(TwoThreeNode *node, int tabs = 0) {
for (int i = 0; i < tabs; ++i) {
cout << "\t";
}
if (node == NULL) {
cout << "`--> NULL" << endl;
return;
}
cout << "`--> " << node->sibNumber()
<< ": ( " << node->key[0] << ", " << node->key[1] << ")" << endl;
if (!node->isLeaf()) {
++tabs;
print(node->child[0], tabs);
print(node->child[1], tabs);
print(node->child[2], tabs);
}
}
public:
// Constructor
TwoThreeTree() {
root = new TwoThreeNode();
root->child[0] = new TwoThreeNode();
root->child[0]->parent = root;
}
// Insert
bool insert(int data) {
TwoThreeNode *newNode = new TwoThreeNode(data);
TwoThreeNode *spot = root->child[0];
if (spot->child[0] == NULL) {
// First insertion
newNode->parent = spot;
spot->child[0] = newNode;
}
else {
spot = findSpot(spot, data);
if (spot == NULL) return false;
spot->insert(new TwoThreeNode(data), data);
}
return true;
}
// Print
void print() {
print(root->child[0]);
cout << endl;
}
};
// Main function
int main(int argc, char **argv) {
if (argc <= 1) {
cout << argv[0] << ": too few arguments" << endl;
cout << "Usage: " << argv[0] << " filename" << endl;
exit(1);
}
// Open file
ifstream infile;
infile.open(argv[1]);
// Create tree and insert data
TwoThreeTree ttTree;
int x;
while (infile.good()) {
infile >> x;
if (!infile.eof()) {
cout << x << endl;
ttTree.insert(x);
ttTree.print();
}
}
infile.close();
return 0;
}
So I am able to insert numbers into my tree using a text file but now I need a function to help me search for a node Any pointers on how I can get started?
Really would appreciate the help, thanks!

Answer 1

Looks like you're pretty close. If you know how a linked list is searched, it is a similar process.
List:
while (this_node.value != search_term)
this_node = this_node.next;
A 2-3 tree is a bit more complex:
while (this_node.value != search_term)
pick_which_node_is_next();
It looks from your code like you can handle this, no problem.