Find Leaves of Binary Tree

Round 1

Questions: Given the root of a binary tree, collect and remove all of its leaves in a top-down manner, and repeat the process until the tree becomes empty. You should return a list of lists where:

• The first list contains all leaves removed in the first round.
• The second list contains all leaves removed in the second round.
• And so on, until the tree is empty.

Example 1
Input:

    1
   / \
  2   3
 / \   \
4   5   6

Output:

[[4,5,6],[2,3],[1]]

Explanation:

1. First round: Remove leaves [4,5,6], remaining tree:

    1
   / \
  2   3

2. Second round: Remove leaves [2,3], remaining tree:

    1

3. Third round: Remove root [1], tree is now empty.

Example 2
Input:

    1
   /
  2
 / 
3

Output:

[[3],[2],[1]]

Constraints

• The number of nodes in the tree is in the range [1, 100].
• -100 <= Node.val <= 100

Follow-up
Can you solve this problem in O(n) time complexity?

Candidate's Approach

No approach provided.

Interviewer's Feedback

No feedback provided.

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