Question

Write a method that determines the key of the successor of the root node in a binary search tree.

For any input binary search tree, find the key of successor of the root node.Note: Successor is the node with the next highest key,  should work for any binary search tree - not just the given example input.

#include <iostream>

using namespace std;

class Node

{

private:

int key;

string val;

Node* left;

Node* right;

friend class BinarySearchTree;

};

class BinarySearchTree

{

public:

BinarySearchTree();

void insert(int key, string val); // Recursive

int rootSuccessor(); // Returns key of the successor of the root, -1 if no

successor

private:

Node* root;

void insertHelper(Node* parent, Node* new_node);

};

int main() {

BinarySearchTree t;

t.insert(5, "Boron");

t.insert(3, "Lithium");

t.insert(7, "Nitrogen");

t.insert(2, "Helium");

t.insert(4, "Berylium");

t.insert(6, "Carbon");

t.insert(8, "Oxygen");

int succ = t.rootSuccessor();

if (succ != -1)

cout << "Successor: " << succ << endl;

else

cout << "No successor" << endl;

}

BinarySearchTree::BinarySearchTree()

{

root = nullptr;

}

void BinarySearchTree::insert(int key, string val)

{

Node* new_node = new Node;

new_node->key = key;

new_node->val = val;

new_node->left = nullptr;

new_node->right = nullptr;

if (root == nullptr) {

root = new_node;

} else {

insertHelper(root, new_node);

}

}

void BinarySearchTree::insertHelper(Node* parent, Node* new_node)

{

if (new_node->key < parent->key) {

if (parent->left == nullptr) {

parent->left = new_node;

}

else {

insertHelper(parent->left, new_node); }

}

else if (new_node->key > parent->key) {

if (parent->right == nullptr) {

parent->right = new_node;

}

else {

insertHelper(parent->right, new_node);

}

}

}

int BinarySearchTree::rootSuccessor() {

// Your code here

}

Answer 1

Please find the answer below for the api rootSuccessor.

Note:

In the below full program,I have modified the insert with different key values to verify whether it works all kinds of key values.

Function only:

int BinarySearchTree::rootSuccessor()
{
//assign th root node to temp and traverse right only to identify the
//next highest key value, which is the root successor.
Node* temp = root;

if(temp != NULL)
{
while (temp->right != NULL)
temp = temp->right;     
return (temp->key);
}
else
{
return -1;
}

}

Full Program:

#include <iostream>

using namespace std;

class Node
{
private:
int key;
string val;
Node* left;
Node* right;
friend class BinarySearchTree;
};

class BinarySearchTree
{
public:
BinarySearchTree();
void insert(int key, string val); // Recursive
int rootSuccessor(); /* Returns key of the successor of the root, -1 if nosuccessor*/

private:
Node* root;

void insertHelper(Node* parent, Node* new_node);

};

int main() {

BinarySearchTree t;

//i have modified the insert to verify whether it works all kinds of key values.

t.insert(8, "Oxygen");
t.insert(5, "Boron");
t.insert(3, "Lithium");
t.insert(17, "Nitrogen");
t.insert(2, "Helium");
t.insert(4, "Berylium");
t.insert(6, "Carbon");

int succ = -1;

succ = t.rootSuccessor();

if (succ != -1)
cout << "Successor: " << succ << endl;
else
cout << "No successor" << endl;
}

BinarySearchTree::BinarySearchTree()
{
root = nullptr;
}

void BinarySearchTree::insert(int key, string val)
{

Node* new_node = new Node;
new_node->key = key;
new_node->val = val;
new_node->left = nullptr;
new_node->right = nullptr;

if (root == nullptr) {
root = new_node;
} else {

insertHelper(root, new_node);
}
}

void BinarySearchTree::insertHelper(Node* parent, Node* new_node)
{

if (new_node->key < parent->key) {

if (parent->left == nullptr) {

parent->left = new_node;

}
else {
insertHelper(parent->left, new_node);
}
}
else if (new_node->key > parent->key)
{
if (parent->right == nullptr)
{
parent->right = new_node;
}
else {
insertHelper(parent->right, new_node);
}
}
}

int BinarySearchTree::rootSuccessor()
{
//assign th root node to temp and traverse right only to identify the
//next highest key value, which is the root successor.
Node* temp = root;

if(temp != NULL)
{
while (temp->right != NULL)
temp = temp->right;
  
return (temp->key);
}
else
{
return -1;
}

}

Output:

Successor: 17

Screen Shot: