Introduction to Sets-HackerRank Solution

 Introduction to Sets-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.

>>> 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.

Average=1355/8=169.375

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Symmetric Difference-HackerRank Solution

 Symmetric Difference-HackerRank Solution

 Objective
Today, we're learning about a new data type: sets.

Concept

If the inputs are given on one line separated by a space character, use split() to get the separate values in the form of a list:

>> a = raw_input()
5 4 3 2
>> lis = a.split()
>> print (lis)
['5', '4', '3', '2']

If the list values are all integer types, use the map() method to convert all the strings to integers.

>> newlis = list(map(int, lis))
>> print (newlis)
[5, 4, 3, 2]

Sets are an unordered bag of unique values. A single set contains values of any immutable data type.

CREATING SETS

>> myset = {1, 2} # Directly assigning values to a set
>> myset = set()  # Initializing a set
>> myset = set(['a', 'b']) # Creating a set from a list
>> myset
{'a', 'b'}

MODIFYING SETS

Using the add() function:

>> myset.add('c')
>> myset
{'a', 'c', 'b'}
>> myset.add('a') # As 'a' already exists in the set, nothing happens
>> myset.add((5, 4))
>> myset
{'a', 'c', 'b', (5, 4)}

Using the update() function:

>> myset.update([1, 2, 3, 4]) # update() only works for iterable objects
>> myset
{'a', 1, 'c', 'b', 4, 2, (5, 4), 3}
>> myset.update({1, 7, 8})
>> myset
{'a', 1, 'c', 'b', 4, 7, 8, 2, (5, 4), 3}
>> myset.update({1, 6}, [5, 13])
>> myset
{'a', 1, 'c', 'b', 4, 5, 6, 7, 8, 2, (5, 4), 13, 3}

REMOVING ITEMS

Both the discard() and remove() functions take a single value as an argument and removes that value from the set. If that value is not present, discard() does nothing, but remove() will raise a KeyError exception.

>> myset.discard(10)
>> myset
{'a', 1, 'c', 'b', 4, 5, 7, 8, 2, 12, (5, 4), 13, 11, 3}
>> myset.remove(13)
>> myset
{'a', 1, 'c', 'b', 4, 5, 7, 8, 2, 12, (5, 4), 11, 3}

COMMON SET OPERATIONS Using union(), intersection() and difference() functions.

>> a = {2, 4, 5, 9}
>> b = {2, 4, 11, 12}
>> a.union(b) # Values which exist in a or b
{2, 4, 5, 9, 11, 12}
>> a.intersection(b) # Values which exist in a and b
{2, 4}
>> a.difference(b) # Values which exist in a but not in b
{9, 5}

The union() and intersection() functions are symmetric methods:

>> a.union(b) == b.union(a)
True
>> a.intersection(b) == b.intersection(a)
True
>> a.difference(b) == b.difference(a)
False

These other built-in data structures in Python are also useful.

Task
Given  sets of integers,  and , print their symmetric difference in ascending order. The term symmetric difference indicates those values that exist in either  or  but do not exist in both.

Input Format

The first line of input contains an integer, .
The second line contains  space-separated integers.
The third line contains an integer, .
The fourth line contains  space-separated integers.

Output Format

Output the symmetric difference integers in ascending order, one per line.

Sample Input

4
2 4 5 9
4
2 4 11 12

Sample Output

5
9
11
12

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