Flatten Binary Tree to Linked List — Step-by-Step Visualization

Algorithm Pattern

In-Place Preorder Flattening

Key Idea

For each node with left child, attach right subtree to leftmost right node, then move left to right.

Step-by-Step Approach

1. While node has left child
2. Find rightmost node of left subtree
3. Attach node.right to rightmost.right
4. Move node.left to node.right
5. Set node.left = null
6. Advance to node.right