114. Flatten Binary Tree to Linked List
Medium
Description
Given the root
of a binary tree, flatten the tree into a "linked list":
-
The "linked list" should use the same
TreeNode
class where theright
child pointer points to the next node in the list and theleft
child pointer is alwaysnull
. -
The "linked list" should be in the same order as a pre-order traversal of the binary tree.
Example 1:
Example 2:
Example 3:
Constraints:
- The number of nodes in the tree is in the range
[0, 2000]
. -100 <= Node.val <= 100
Follow up: Can you flatten the tree in-place (with O(1)
extra space)?
Solutions