Grokking LinkedIn Coding Interview
Ask Author
Back to course home

0% completed

Vote For New Content

Find Leaves of Binary Tree (medium)
Table of Contents

Problem Statement

Examples

Try it yourself

Problem Statement

Given the root of a binary tree, collect a tree's leaf nodes by following the given rules and return them in a 2D array.

  • Collect all the leaf nodes from the left to right.
  • Remove all the leaf nodes.
  • Repeat until the tree is empty.

Examples

  • Example 1:
    • Input: root = [1,2,3,4]
Image

  • Expected Output: [[4,3],[2],[1]]

  • Justification: Initially, nodes 4 and 3 are leaves and are removed in the first round. In the second round, node 2 becomes a leaf. Node 1 is the last one remaining and is removed in the final round.

  • Example 2:

    • Input: root = [1,2,3,null, null,4,5,null, null,6,null]
Image

  • Expected Output: [[2,4,6],[5],[3],[1]]

  • Justification: In the first round, the leaves are nodes 2, 4, and 6. Once removed, node 5 becomes the leaf in the second round, and then node 3 becomes the leaf node in the third round. Finally, node 1 is left and removed in the last round.

  • Example 3:

    • Input: root = [1,2,null,3,null,4]
Image
  • Expected Output: [[4],[3],[2],[1]]
  • Justification: This tree has a linear structure. Each node becomes a leaf one after the other, starting from node 4 to node 1.

Try it yourself

Try solving this question here:

Python3
Python3
. . . .
Mark as Completed

Table of Contents

Problem Statement

Examples

Try it yourself