Construct Binary Tree from Preorder and Inorder Traversal

• Tree
• Recursion

Those two are the keys for the approach.

• The first element of pre-order traverse is always the root node.
• The left side and the right side of the root node in in-order traverse is its left sub-tree and its right sub-tree

1. First, set the first element of pre-order as current root node

• then take it out from the array

2. Find the index of the root node from in-order array.

• left side becomes its left sub-tree
• right side becomes its right sub-tree

4. Repeat 1 & 2 on the left sub-tree and the right sub-tree

• until no element is left in either pre-ordere array or in-order array