# List Length – HackerRank Solution

In this post, we will solve List Length HackerRank Solution. This problem (List Length) is a part of HackerRank Functional Programming language.

Count the number of elements in an array without using count, size or length operators (or their equivalents). The input and output portions will be handled automatically by the grader. You only need to write a function with the recommended method signature.

## Input Format

A list of N integers, each on a separate line.

## Output Format

Output a single integer N, the length of the list that was provided as input.

Sample Input

``````2
5
1
4
3
7
8
6
0
9``````

Sample Output

``10``

## Constraints

• 0 <= N <= 100
• Each element, X, in the list: 0 <= X <= 100

Recommended Method Signature

``````Number Of Parameters: 1
Parameters: [list]
Returns: Number``````

For Hackers Using Clojure

This will be the outline of your function body (fill in the blank portion marked by underscores):

`` (fn[lst]___________________________)``

For Hackers Using Scala

This will be the outline of your function body (fill in the blank portion marked by underscores):

`` def f(arr:List[Int]):Int = __________________``

This will be the outline of your function body (fill in the blank portion marked by underscores):

`` len lst = __________________  ``

For Hackers Using other Languages

You have to read input from standard input and write output to standard output. Please follow the input/output format mentioned above.

NOTE: You only need to submit the code above after filling in the blanks appropriately. The input and output section will be handled by us. The focus is on writing the correct function.

## Solution – List Length – HackerRank Solution

Scala

```def f(arr: List[Int]): Int = {
@scala.annotation.tailrec
def inner(arr: List[Int], acc: Int = 0): Int = arr match {
case Nil => acc
case _ :: xs => inner(xs, acc + 1)
}

inner(arr)
}
```

Note: This program (List Length) is generated by HackerRank but the solution is provided by CodingBroz. This tutorial is only for Educational and Learning purpose.