Populating Next Right Pointers in Each Node
You are given a perfect binary tree, and the task is to populate each ’next’ pointer to point to its next right node. Since it’s a perfect binary tree, every parent node has two children, and all leaves are on the same level.
The algorithm can be implemented using a recursive function. Here’s a stepbystep guide:
 Base Case: If the root is
null
, return immediately as there’s nothing to do.  Connection to Immediate Right: If the root’s left child is not
null
, connect the root’s left child’snext
pointer to the root’s right child.  Connection Across Siblings: If the root’s
next
pointer is notnull
, connect the root’s right child’snext
pointer to thenext
pointer of the root’s left child.  Recursion: Call the function recursively for the left and right children of the root.


Key Takeaways:
 The recursion follows the pattern of a preorder traversal (rootleftright).
 The time complexity is (O(n)), where (n) is the number of nodes in the tree, since every node is visited once.
 The space complexity is (O(\log n)) for the recursion stack since the binary tree is perfect.
Define the Terms perfect binary tree All leaves are on the same level, and every parent has two children.
Define the Interface Input: root Output: root
Analyze the Input and Output
Identify the Invariants
Identify the constraints
 The number of nodes in the given tree is less than 4096.
 1000 <= node.val <= 1000
Search the Problem Space
Classify the Problem
Analyze the Examples
Solve the Problem by Hand
What traversal strategy?
 BFS (Problem requires to create links at every level) [root] [2,3] [4, 5, 6, 7] Can we keep them in a queue? (FIFO)
Establish the next links
Describe the Pattern
Distill the Observations to Create Insights
Brute Force Approach


Define the Terms perfect binary tree All leaves are on the same level, and every parent has two children.
Define the Interface Input: root Output: root
Analyze the Input and Output
Identify the Invariants
Identify the constraints
 The number of nodes in the given tree is less than 4096.
 1000 <= node.val <= 1000
Search the Problem Space
Classify the Problem
Analyze the Examples
Solve the Problem by Hand
What traversal strategy?
 BFS (Problem requires to create links at every level) [root] [2,3] [4, 5, 6, 7] Can we keep them in a queue? (FIFO)
Establish the next links
Describe the Pattern
Distill the Observations to Create Insights
Brute Force Approach

