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Grokking the Coding Interview Patterns in Python

Populating Next Right Pointers in Each Node

Explore how to connect every node to its immediate right node in a perfect binary tree using breadth-first search. Understand the concept of setting next pointers to link nodes at the same level efficiently. This lesson teaches you the step-by-step approach to implement the solution within given constraints and test your code by verifying these connections.

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Statement

Given a perfect binary treeA binary tree in which all the levels are completely filled with nodes, and all leaf nodes (nodes with no children) are at the same level., where each node contains an additional pointer called next. This pointer is initially set to NULL for all nodes. Your task is to connect all nodes of the same hierarchical level by setting the next pointer to its immediate right node.

The next pointer of the rightmost node at each level is set to NULL.

Constraints:

  • The number of nodes in the tree is in the range [0,500][0, 500].
  • −1000≤-1000 \leq Node.data ≤1000\leq 1000

Examples

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Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

Populating Next Right Pointers in Each Node

1.

What should be in the next of the node value 15 after making the connections of the tree at every level?

         _______ 25 _______
        |                  |
     __ 14 _            __ 35__
    |       |          |       |
  _ 1_    _ 15 _     - 20 -   200
 |    |  |      |   |      |  |  |
 8    9  10     11  6      7  2  5
A.

20

B.

1

C.

11

D.

200

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Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
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Try it yourself

Implement your solution in connect_next_right.py in the following coding playground. You’ll need the provided supporting code to implement your solution.

Note: We have set up the test cases to check the next right nodes of the output tree with connected nodes at each level.

Python
usercode > connect_next_right.py
from EduBinaryTree import *
from EduTreeNode import *
def populate_next_pointers(root):
    # Replace this placeholder return statement with your code
    
    return root
Populating Next Right Pointers in Each Node