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LeetCode 105: Tree-Building Hack That's Half-Baked

Binary trees from traversals sound smart. Until the code's sloppy recursion bites back with quadratic doom.

theAIcatchup Apr 09, 2026 3 min read
Step-by-step visual trace of LeetCode 105 binary tree construction from preorder and inorder arrays

⚡ Key Takeaways

  • Default solution is O(n²)—fine for interviews, fatal for scale. 𝕏
  • Hashmap indices make it O(n) time and space. 𝕏
  • LeetCode 105 tests core recursion; optimize to impress. 𝕏
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#binary tree #leetcode-105 #recursion #tree-construction

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Originally reported by Dev.to

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