Leetcode - 105. Construct Binary Tree from Preorder and Inorder Traversal

The text discusses two methods for constructing a binary tree from its preorder and inorder traversals. The first, a naive recursive approach, uses `slice()` and `indexOf()` which leads to an O(n²) time complexity. This simple method identifies the root, finds its position in the inorder array, and recursively constructs left and right subtrees. Repeated array slicing causes additional overhead in the naive method. The naive approach has a space complexity of O(n) due to recursion and sliced arrays. The second approach is optimized, leveraging a hash map and index pointers for efficiency. This optimized method uses a hash map for constant-time lookups of node indices in the inorder traversal. Index pointers replace slicing, avoiding unnecessary array copying in the optimized method. The optimized approach achieves a time complexity of O(n) by avoiding repeated array operations. Space complexity remains O(n) for the hash map and recursion in the optimized version. The optimized approach is considerably faster than the naive implementation. In summary, using a hash map and index pointers provides significant performance benefits.