HackerRank Python Solution - Sets - Introduction to Sets

• 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.

• The formula used:

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].

Constraints:

• 0 < N <= 100

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

• Average = 1355/8 = 169.375

Solution:

def average(array):
    arr_set = set(array)
    N = len(arr_set)
    Total = sum(arr_set)
    return Total/N
    
if __name__ == '__main__':
    n = int(input())
    arr = list(map(int, input().split()))
    result = average(arr)
    print(result)

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