Construct Binary Tree from Preorder and Inorder Traversal

105. Construct Binary Tree from Preorder and Inorder Traversal

Solutions

The solution is similar to divide and conquer.

1. Find the root by using pre-order traversal. Find the root’s index in in-order traversal.
2. Divide in-order by the index and continue.
   Optimization Can use dictionary to store the index of in-order array {num: idx} and use iterater for pre-order traversal.