Problem

Link to the original HackerRank problem

We have seen the applications of union, intersection, difference and symmetric difference operations, but these operations do not make any changes or mutations to the set.

We can use the following operations to create mutations to a set:

• .update() or |=

  • Update the set by adding elements from an iterable/another set.

    >>> H = set("Hacker")
    >>> R = set("Rank")
    >>> H.update(R)
    >>> print H
    set(['a', 'c', 'e', 'H', 'k', 'n', 'r', 'R'])
    

• .intersection_update() or &=

  • Update the set by keeping only the elements found in it and an iterable/another set.

    >>> H = set("Hacker")
    >>> R = set("Rank")
    >>> H.intersection_update(R)
    >>> print H
    set(['a', 'k'])
    

• .difference_update() or -=

  • Update the set by removing elements found in an iterable/another set.

    >>> H = set("Hacker")
    >>> R = set("Rank")
    >>> H.difference_update(R)
    >>> print H
    set(['c', 'e', 'H', 'r'])
    

• .symmetric_difference_update() or ^=

  • Update the set by only keeping the elements found in either set, but not in both.

    >>> H = set("Hacker")
    >>> R = set("Rank")
    >>> H.symmetric_difference_update(R)
    >>> print H
    set(['c', 'e', 'H', 'n', 'r', 'R'])
    

TASK

• You are given a set A and N number of other sets.
• These N number of sets have to perform some specific mutation operations on set A.
• Your task is to execute those operations and print the sum of elements from set A.

Input Format

• The 1st line contains the number of elements in set A.
• The 2nd line contains the space separated list of elements in set A.
• The 3rd line contains integer N, the number of other sets.
• The next 2 * N lines are divided into n parts containing two lines each:
  • The 1st line of each part contains the space separated entries of the operation name and the length of the other set.
  • The 2nd line of each part contains space separated list of elements in the other set.

Constraints

• 0 <= len(set(A)) <= 1,000
• 0 <= len(otherSets) <= 100
• 0 <= N <= 100

Output Format

Output the sum of elements in set A.

Sample Input

16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 24 52
4
intersection_update 10
2 3 5 6 8 9 1 4 7 11
update 2
55 66
symmetric_difference_update 5
22 7 35 62 58
difference_update 7
11 22 35 55 58 62 66

Sample Output 0

38

Explanation

After the

• 1st operation, (intersection_update operation), we get: set A = set([1, 2, 3, 4, 5, 6, 7, 8, 9 ,11])
• 2nd operation, (update operation), we get: set A = set([1, 2, 3, 4, 5, 6, 7, 8, 9 , 11, 55, 66])
• 3rd operation, (symmetric_difference_update operation), we get: set A = set([1, 2, 3, 4, 5, 6, 7, 8, 9 , 11, 55, 62, 66])
• 4th operation, (difference_update operation), we get: set A = set([1, 2, 3, 4, 5, 6, 7, 8, 9])

The sum of elements in set A after these operations is 38.

Code

Starter

if __name__ == '__main__':
    n = int(input())
    student_marks = {}
    for _ in range(n):
        name, *line = input().split()
        scores = list(map(float, line))
        student_marks[name] = scores
    query_name = input()

Solution

The implementation is pretty straightforward, we can just translate 1:1 the instructions:

if __name__ == '__main__':
    a_n = int(input())
    a = set(map(int, input().split()))
    o_n = int(input())
    for _ in range(o_n):
        operation, n_str = input().split()
        n = int(n_str)
        s = set(map(int, input().split()))
        if operation == 'update':
            a.update(s)
        elif operation == 'intersection_update':
            a.intersection_update(s)
        elif operation == 'symmetric_difference_update':
            a.symmetric_difference_update(s)
        elif operation == 'difference_update':
            a.difference_update(s)
    print(sum(a))

We can make the above implementation slightly terser using the Python structural pattern matching match ... case:

if __name__ == '__main__':
    a_n = int(input())
    a = set(map(int, input().split()))
    o_n = int(input())
    for _ in range(o_n):
        operation, n_str = input().split()
        n = int(n_str)
        s = set(map(int, input().split()))
        match operation:
            case 'update':                      a |= s # a.update(s)
            case 'intersection_update':         a &= s # a.intersection_update(s)
            case 'difference_update':           a -= s # a.difference_update(s)
            case 'symmetric_difference_update': a ^= s # a.symmetric_difference_update(s)
    print(sum(a))

Key Takeways