Iterative_inorder.cpp

// C++ program to print inorder traversal
// using stack.
#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;
    Node (int data)
    {
        this->data = data;
        left = right = NULL;
    }
};
 
/* Iterative function for inorder tree
   traversal */
void inOrder(struct Node *root)
{
    stack<Node *> s;
    Node *curr = root;
 
    while (curr != NULL || s.empty() == false)
    {
        /* Reach the left most Node of the
           curr Node */
        while (curr !=  NULL)
        {
            /* place pointer to a tree node on
               the stack before traversing
              the node's left subtree */
            s.push(curr);
            curr = curr->left;
        }
 
        /* Current must be NULL at this point */
        curr = s.top();
        s.pop();
 
        cout << curr->data << " ";
 
        /* we have visited the node and its
           left subtree.  Now, it's right
           subtree's turn */
        curr = curr->right;
 
    } /* end of while */
}
 
/* Driver program to test above functions*/
int main()
{
 
    /* Constructed binary tree is
              1
            /   \
          2      3
        /  \
      4     5
    */
    struct Node *root = new Node(1);
    root->left        = new Node(2);
    root->right       = new Node(3);
    root->left->left  = new Node(4);
    root->left->right = new Node(5);
 
    inOrder(root);
    return 0;
}