HackerRank Python: Introduction to Sets Solution

Table of Contents

Question

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 total number of plants.
The second line contains the N space separated heights of the plants.

Constraints

0<N<=1000

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 is the set containing the distinct heights. Using the sum() and len() functions, we can compute the average.

Solution

				
					def average(array):
    s=set(array)
    return sum(s)/len(s)

if __name__ == '__main__':
    n = int(input())
    arr = list(map(int, input().split()))
    result = average(arr)
    print(result)

Explanation

This code defines a function named average that calculates the average of a given array of numbers. Here’s a step-by-step explanation of the code:

The function average takes an array as input.
It creates a set s from the array by using the set() function. This eliminates any duplicate values in the array, as sets only store unique elements.
The sum of the elements in the set s is calculated using the sum() function.
The length of the set s is calculated using the len() function.
The sum of the elements is divided by the length of the set to obtain the average.
The average value is then returned by the function.

The code also includes a block that executes when the script is run directly (not imported as a module):

It prompts the user to enter an integer n using the input() function.
It reads a line of space-separated numbers from the user and converts them into a list of integers using the map() and split() functions.
The average function is called with the obtained list as an argument, and the result is assigned to the variable result.
Finally, the calculated average is printed to the console using the print() function.