InorderTraversalIterative.cpp

// Inorder Traversal (Iterative) 

// Given a binary tree. Find the inorder traversal of the tree without using recursion.

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


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

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


// 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 Code Ends
//User function Template for C++

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

class Solution {
public:
    vector<int> inOrder(Node* root)
    {
        //code here
        vector<int>ans;
        stack<Node*>s;
        if(root==NULL){
            return ans;
        }
        Node * curr = root;
        while(curr!=NULL || !s.empty()){
            while(curr!=NULL){
                s.push(curr);
                curr=curr->left;
            }
            ans.push_back(s.top()->data);
            curr=s.top()->right;
            s.pop();
        }
        return ans;
    }
};

// { Driver Code Starts.

/* Driver program to test size function*/

  

int main() {

   
    int t;
    scanf("%d ", &t);
    while (t--) {
        string s, ch;
        getline(cin, s);
        
        Node* root = buildTree(s);

        vector<int> ans;
        Solution ob;
        ans = ob.inOrder(root) ;

        for (int i = 0; i < ans.size(); i++)
            cout << ans[i] << " ";

        cout << endl;
     
    }
    return 0;
}
  // } Driver Code Ends