# Leetcode 105 - Construct binary tree from preorder and inorder traversal

`Note:`

- The return value is the root, so we need to return
`node`

in the recursion function. - The
`first`

element of`preorder`

is the current`root`

. - Split inorder into left and right subtree by the value of
`root`

. (All vals are unique) - Know how to assign
`root`

‘s left and right subtree, then by the`length`

of left and right`inorder`

, split`preorder`

into left and right subtree.

`Question:`

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.

`Example:`

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

`Code:`

1 | /** |