Kamal Awasthi

Kamal Awasthi

I am in eternal love with Poetry, Philosophies & Coding. Read my poems @inklins.me. To read more about me head to About section.

Given a binary tree, we have to find the pre-order of it. We will do this with the help of while loop(iterative-solution).

We will take a stack to save the node and then read them one by one by popping them and then going right to it.

Below is the function to perform a non-recursive pre-order solution:

void preOrder(BinaryTreeNode *root){
    stack <BinaryTreeNode*> s;
    while(1){
        while(root){
            //process the curren node
            cout<<root->data;
            s.push(root);
            root=root->left;
        }
        if(s.empty())
            break; //if stack is empty, then break
        root=s.top();
        s.pop();
        root=root->right;
    }
}

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