176.cpp

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

/* A binary tree node has data, pointer to left child
   and a pointer to right child */
struct Node
{
    int data;
    struct Node* left;
    struct Node* right;
};
// Utility function to create a new Tree Node
Node* newNode(int val)
{
    Node* temp = new Node;
    temp->data = val;
    temp->left = NULL;
    temp->right = NULL;
    
    return temp;
}

 // } Driver Code Ends
/* A binary tree Node

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


class Solution
{
    public:
    
    
    
    vector <vector <int>> result;

void levelOrderInLevels(Node* root){
	if(!root) return;
	queue<Node *> q;
	q.push(root);
	while(!q.empty()){
		int sz=q.size();
		vector<int> level;
		while(sz--){
			Node * x=q.front();
			q.pop();
				if(x->left) q.push(x->left);
				if(x->right) q.push(x->right);
				level.push_back(x->data);
			
		}
		result.push_back(level);
	}
}

    
    
    vector<int> levelOrder(Node* node)
    {
      queue<Node *> q;
      q.push(node);
      vector<int> res;
      while(!q.empty()){
          Node *temp=q.front();
          res.push_back(temp->data);
          q.pop();
          if(temp->left) q.push(temp->left);
          if(temp->right) q.push(temp->right);
      }
      return res;
    }
};

// { Driver Code Starts.

/* Helper function to test mirror(). Given a binary
   search tree, print out its data elements in
   increasing sorted order.*/
void inOrder(struct Node* node)
{
  if (node == NULL)
    return;

  inOrder(node->left);
  printf("%d ", node->data);

  inOrder(node->right);
}

// 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 = newNode(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 = newNode(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 = newNode(stoi(currVal));
                
            // Push it to the queue
            queue.push(currNode->right);
        }
        i++;
    }
    
    return root;
}

/* Driver program to test size function*/
int main()
{
  int t;
  scanf("%d ",&t);
  while (t--)
  {
        string s;
		getline(cin,s);
		Node* root = buildTree(s);
		Solution ob;
        vector <int> res = ob.levelOrder(root);
        for (int i : res) cout << i << " ";
        cout << endl;
  }
  return 0;
}


  // } Driver Code Ends