130. Construct Binary Tree from Preorder and Inorder Traversal

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Input: preorder = [3,9,20,15,7], inorder = [9,3,15,20,7]

Output: [3,9,20,null,null,15,7]

Explanation: The tree is constructed as follows: Root is 3. Left subtree has root 9. Right subtree has root 20, with left child 15 and right child 7.

Input: preorder = [-1], inorder = [-1]

Output: [-1]

Explanation: The tree consists of a single node with value -1.

Time Complexity

O(n)

Space Complexity

O(n)