Learn

Constraints are placed on the data or node arrangement of a tree to solve difficult problems like efficient search.

A *binary tree* is a type of tree where each parent can have **no more than two children**, known as the *left child* and *right child*.

Further constraints make a *binary search tree*:

- Left child values must be lesser than their parent.
- Right child values must be greater than their parent.

The constraints of a binary search tree allow us to search the tree efficiently. At each node, we can discard **half** of the remaining possible values!

Let’s walk through locating the value `31`

.

- Start at the root:
`39`

`31`

<`39`

, we move to the left child:`23`

`23`

<`31`

, we move to the right child:`35`

`31`

<`35`

, we move to the left child:`31`

- We found the value
`31`

!

In a dataset of **fifteen** elements, we only made **three** comparisons. What a deal!

### Instructions

From the root, follow a node’s left or right child to find the following numbers: `22`

, `42`

, `97`

.

How many steps did each number take?

# Sign up to start coding

By signing up for Codecademy, you agree to Codecademy's Terms of Service & Privacy Policy.