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1194. Path In Zigzag Labelled Binary Tree

My accepted Python solution to LeetCode problem 1194, Path In Zigzag Labelled Binary Tree, running in 0ms.

  • Difficulty: Medium
  • Python
  • Runtime 0ms
  • Memory 17.4MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 0ms, memory 17.4MB, accepted 2026-01-02.

python
class Solution:
    def pathInZigZagTree(self, label: int) -> List[int]:
        # First, find the level of the label
        level = 0
        n = label
        while n > 0:
            n //= 2
            level += 1
        
        result = []
        
        while label >= 1:
            result.append(label)
            
            # Move to parent
            # First, find the "normal" position at this level
            # Level starts from 1: level 1 has 1 node, level 2 has 2, etc.
            level_start = 2 ** (level - 1)
            level_end = 2 ** level - 1
            
            # If this level is "reversed" (even levels are reversed, 1-indexed)
            # The zigzag pattern alternates: level 1 is normal, level 2 reversed, level 3 normal, etc.
            
            # Find the "mirror" position
            mirror_label = level_start + level_end - label
            
            # Parent of mirror position in normal tree
            parent = mirror_label // 2
            
            label = parent
            level -= 1
        
        return result[::-1]

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