# Introduction to Sets in Python - HackerRank Solution

# Problem

Python set hackerrank solution

A set is an unordered collection of elements without duplicate entries.

When printed, iterated or converted into a sequence, its elements will appear in an arbitrary order.

**Example**

>>> print set() set([]) >>> print set('HackerRank') set(['a', 'c', 'e', 'H', 'k', 'n', 'r', 'R']) >>> print set([1,2,1,2,3,4,5,6,0,9,12,22,3]) set([0, 1, 2, 3, 4, 5, 6, 9, 12, 22]) >>> print set((1,2,3,4,5,5)) set([1, 2, 3, 4, 5]) >>> print set(set(['H','a','c','k','e','r','r','a','n','k'])) set(['a', 'c', 'r', 'e', 'H', 'k', 'n']) >>> print set({'Hacker' : 'DOSHI', 'Rank' : 616 }) set(['Hacker', 'Rank']) >>> print set(enumerate(['H','a','c','k','e','r','r','a','n','k'])) set([(6, 'r'), (7, 'a'), (3, 'k'), (4, 'e'), (5, 'r'), (9, 'k'), (2, 'c'), (0, 'H'), (1, 'a'), (8, 'n')])

Basically, sets are used for membership testing and eliminating duplicate entries.

Task

Now, let's use our knowledge of sets and help Mickey.

Ms. Gabriel Williams is a botany professor at District College. One day, she asked her student Mickey to compute the average of all the plants with distinct heights in her greenhouse.

Formula used:

**Average = Sum of Distinct Heights / Total Number of Distinct Heights**

Function Description

Complete the average function in the editor below.

average has the following parameters:

- int arr: an array of integers

Returns

- float: the resulting float value rounded to 3 places after the decimal

Input Format

The first line contains the integer, **N**, the size of **arr**.

The second line contains the **N** space-separated integers, **arr[i]**.

Sample Input

STDIN Function ----- -------- 10 arr[] size N = 10 161 182 161 154 176 170 167 171 170 174 arr = [161, 181, ..., 174]

Sample Output

169.375

Explanation

Here, set [161, 167, 170, 171, 174, 176, 182, 154] is the set containing the distinct heights. Using the sum() and len() functions, we can compute the average.

**Average = 1355 / 8 = 169.375**