Inorder_tree.cpp

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

struct Node
{
    int data;
    struct Node* left;
    struct Node* right;
    Node (int data)
    {
        this->data = data;
        left = right = NULL;
    }
};

void inOrder(struct Node *root)
{
    stack<Node *> s;
    Node *curr = root;

    while (curr != NULL || s.empty() == false)
    {
        while (curr !=  NULL)
        {
            s.push(curr);
            curr = curr->left;
        }

        curr = s.top();
        s.pop();

        cout << curr->data << " ";

        curr = curr->right;

    }
}

int main()
{
    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;
}