Populating Next Right Pointers in Each Node

Medium(https://leetcode.com/problems/populating-next-right-pointers-in-each-node/submissions/)

You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition:

Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.

Initially, all next pointers are set to NULL.

Follow up:

  • You may only use constant extra space.
  • Recursive approach is fine, you may assume implicit stack space does not count as extra space for this problem.

Example 1:

Constraints:

  • The number of nodes in the given tree is less than 4096.
  • -1000 <= node.val <= 1000

Solution:

Code:

Complexity Analysis

  • Time Complexity: O(N) since we process each node exactly once. Note that processing a node in this context means popping the node from the queue and then establishing the next pointers.
  • Space Complexity: O(N). This is a perfect binary tree which means the last level contains N/2 nodes. The space complexity for breadth first traversal is the space occupied by the queue which is dependent upon the maximum number of nodes in particular level. So, in this case, the space complexity would be O(N).

Success

Details

Runtime: 64 ms, faster than 51.47% of Python3 online submissions for Populating Next Right Pointers in Each Node.

Memory Usage: 15.8 MB, less than 23.04% of Python3 online submissions for Populating Next Right Pointers in Each Node.

Next to Try:

Populating Next Right Pointers in Each Node II

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