Kth_Smallest_or_Largest_Element_in_BST.cpp

//{ Driver Code Starts
#include <bits/stdc++.h>
using namespace std;
#define MAX_HEIGHT 100000

// Tree Node
struct Node {
    int data;
    Node* left;
    Node* right;

    Node(int val) {
        data = val;
        left = right = NULL;
    }
};

// Function to Build Tree
Node* buildTree(string str) {
    // Corner Case
    if (str.length() == 0 || str[0] == 'N') return NULL;

    // Creating vector of strings from input
    // string after spliting by space
    vector<string> ip;

    istringstream iss(str);
    for (string str; iss >> str;) ip.push_back(str);

    // Create the root of the tree
    Node* root = new Node(stoi(ip[0]));

    // Push the root to the queue
    queue<Node*> queue;
    queue.push(root);

    // Starting from the second element
    int i = 1;
    while (!queue.empty() && i < ip.size()) {

        // Get and remove the front of the queue
        Node* currNode = queue.front();
        queue.pop();

        // Get the current node's value from the string
        string currVal = ip[i];

        // If the left child is not null
        if (currVal != "N") {

            // Create the left child for the current node
            currNode->left = new Node(stoi(currVal));

            // Push it to the queue
            queue.push(currNode->left);
        }

        // For the right child
        i++;
        if (i >= ip.size()) break;
        currVal = ip[i];

        // If the right child is not null
        if (currVal != "N") {

            // Create the right child for the current node
            currNode->right = new Node(stoi(currVal));

            // Push it to the queue
            queue.push(currNode->right);
        }
        i++;
    }

    return root;
}


// } Driver Code Ends
/*Complete the function below

struct Node {
    int data;
    Node *left;
    Node *right;

    Node(int val) {
        data = val;
        left = right = NULL;
    }
};
*/

class Solution {
  public:
    // Return the Kth smallest element in the given BST
    int cnt = 1;
    int ans = -1;
    void inOrder(Node* root, int k)
    {
        if(root == NULL) return;
        inOrder(root->left, k);
        if(k == cnt)
            ans = root->data;
        cnt++;
        inOrder(root->right, k);
    }
    int KthSmallestElement(Node *root, int K) {
        inOrder(root, K);
        return ans;
    }
};

//{ Driver Code Starts.
int main() {

    int t;
    string tc;
    getline(cin, tc);
    t = stoi(tc);
    while (t--) {
        string s;
        getline(cin, s);
        Node* root = buildTree(s);

        getline(cin, s);
        int k = stoi(s);
        //  getline(cin, s);
        Solution obj;
        cout << obj.KthSmallestElement(root, k) << endl;
        // cout<<"~"<<endl;
    }
    return 0;
}
// } Driver Code Ends



// For Finding Kth Largest Element in BST  ( Go Last and check out Solution class )

/*

//{ Driver Code Starts
#include <bits/stdc++.h>
using namespace std;

// Tree Node
struct Node {
    int data;
    Node *left;
    Node *right;

    Node(int val) {
        data = val;
        left = right = NULL;
    }
};

// Function to Build Tree
Node* buildTree(string str)
{   
    // Corner Case
    if(str.length() == 0 || str[0] == 'N')
            return NULL;
    
    // Creating vector of strings from input 
    // string after spliting by space
    vector<string> ip;
    
    istringstream iss(str);
    for(string str; iss >> str; )
        ip.push_back(str);
        
    // Create the root of the tree
    Node* root = new Node(stoi(ip[0]));
        
    // Push the root to the queue
    queue<Node*> queue;
    queue.push(root);
        
    // Starting from the second element
    int i = 1;
    while(!queue.empty() && i < ip.size()) {
            
        // Get and remove the front of the queue
        Node* currNode = queue.front();
        queue.pop();
            
        // Get the current node's value from the string
        string currVal = ip[i];
            
        // If the left child is not null
        if(currVal != "N") {
                
            // Create the left child for the current node
            currNode->left = new Node(stoi(currVal));
                
            // Push it to the queue
            queue.push(currNode->left);
        }
            
        // For the right child
        i++;
        if(i >= ip.size())
            break;
        currVal = ip[i];
            
        // If the right child is not null
        if(currVal != "N") {
                
            // Create the right child for the current node
            currNode->right = new Node(stoi(currVal));
                
            // Push it to the queue
            queue.push(currNode->right);
        }
        i++;
    }
    
    return root;
}


// } Driver Code Ends
/*The Node structure is defined as
struct Node {
    int data;
    Node *left;
    Node *right;

    Node(int val) {
        data = val;
        left = right = NULL;
    }
};
*/
/*

// return the Kth largest element in the given BST rooted at 'root'
class Solution
{
    public:
    vector<int> ans;
    void inOrder(Node* root)
    {
        if(root == NULL) return;
        inOrder(root->left);
        ans.push_back(root->data);
        inOrder(root->right);
    }
    int kthLargest(Node *root, int K)
    {
        inOrder(root);
        return ans[ans.size()-K];
    }
};

//{ Driver Code Starts.

int main()
{
    int t;
    cin>>t;
    getchar();
    
    while(t--)
    {
        string s;
        getline(cin,s);
        Node* head = buildTree(s);
        
        int k;
        cin>>k;
        getchar();
        
        Solution ob;
        cout << ob.kthLargest( head, k ) << endl;
    }
    return 1;
}
// } Driver Code Ends

*/