Good Subtrees (05-05-23).cpp

//{ Driver Code Starts
//Initial Template for C++

#include <bits/stdc++.h>
using namespace std;

struct Node
{
    int data;
    struct Node *left;
    struct 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
//User function Template for C++

class Solution{
public:
    int count = 0;
    
    unordered_set<int> func(Node* root, int k){
        unordered_set<int> s;
        if(!root)
            return s;
        
        auto l = func(root->left, k);

        auto r = func(root->right, k);
        
        //if any of the left sub tree or right sub tree has more than k elements, then
        //no need to combine them because even after combining the result will be same.
        if(r.size()>k)
            return r;
        if(l.size()>k)
            return l;
            
        for( auto x: l){
            s.insert(x);
        }
        for(auto x: r)
            s.insert(x);
        
        s.insert(root->data);
        
        if(s.size()<=k){
            count++;
             
        }
           
        return s;
    }
    
    int goodSubtrees(Node *root,int k){
        func(root, k);
        return count;
    }
};

//{ Driver Code Starts.

int main(){
    int t;
    cin>>t;
    for(int i=0;i<t;i++){
        if(i==0){
            string s;
            getline(cin,s);
        }
        string str;
        getline(cin,str);
        int k;
        cin>>k;
        string newline;
        getline(cin,newline);
        Node* root = buildTree(str);
        Solution ob;
        cout<<ob.goodSubtrees(root,k)<<endl;
    }
    return 0;
}
// } Driver Code Ends