Leetcode 114: Flatten Binary Tree to Linked List

To solve this problem, we can perform a level order traversal of the binary tree and convert it into a linked list. We’ll use a queue to store the nodes at each level and keep track of the previous node in the linked list. Here’s the step-by-step approach to solve this problem:

1. Initialize an empty queue to store the nodes of the binary tree.
2. Initialize three pointers: prev (previous node in the linked list), current (the current node being processed), and next (the next node in the linked list). Set prev to None initially.
3. Enqueue the root node into the queue.
4. While the queue is not empty, repeat steps 5-11.
5. Dequeue a node from the front of the queue and assign it to current.
6. If current has no left child, simply set next to current and skip to step 8.
7. If current has a left child, enqueue the left child into the queue.
8. Set next to the right child of current.
9. If current has no right child, set prev to current and skip to step 10.
10. If current has a right child, enqueue the right child into the queue.
11. Set prev to current.
12. Finally, after the level order traversal, prev will be the head of the flattened linked list. Return prev as the result.