Introduction to Sets - Hacker Rank 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:

Input Format

The first line contains the integer, , the total number of plants.
The second line contains the  space separated heights of the plants.

Constraints

Output Format

Output the average height value on a single line.

Sample Input

10
161 182 161 154 176 170 167 171 170 174

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

Introduction to Sets - Hacker Rank Solution

The approach to solve this challenge follows: 

Step 1: Store the set of inputs in the variable distinctHeights.

Step 2: Store the sum of distinctHeights in the variable sumOfDistinctHeights.

Step 3: Store the total number of distinctHeights in the variable totalDistinctHeights.

Step 4: Take the average by dividing the sumOfDistinctHeights with totalDistinctHeights.

Step 5: Print the output.

Problem Setter's code:

from __future__ import division
n = int(raw_input())
heights = [int(x) for x in raw_input().split()]

#Step 1 - Make Set
distinctHeights = set(heights)

#Step 2 - Summation of Set
sumOfDistinctHeights = sum(distinctHeights)

#Step 3 - Length of Set
totalDistinctHeights = len(distinctHeights)

#Step 4 - Take Average
average = sumOfDistinctHeights/totalDistinctHeights

#Step 5 - Print Output
print average