Construct BT from Preorder and Inorder

Construct Binary Tree from Preorder and Inorder Traversal

Given two integer arrays preorder and inorder where preorder is the preorder traversal of a binary tree and inorder is the inorder traversal of the same tree, construct and return the binary tree.

Examples

Example 1:

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

      3
     / \
    9  20
       / \
      15   7

Example 2:

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

Constraints

• 1 <= preorder.length <= 3000
• inorder.length == preorder.length
• -3000 <= preorder[i], inorder[i] <= 3000
• preorder and inorder consist of unique values.
• Each value of inorder also appears in preorder.

Expected Complexity

• Time: O(n)
• Space: O(n)