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Set .discard(), .remove() & .pop() Solution

Set .discard(), .remove() & .pop() Solution

Beeze Aal
Beeze Aal

.remove(x)

This operation removes element  from the set.
If element  does not exist, it raises a KeyError.
The .remove(x) operation returns None.

Example>>> s = set([1, 2, 3, 4, 5, 6, 7, 8, 9]) >>> s.remove(5) >>> print s set([1, 2, 3, 4, 6, 7, 8, 9]) >>> print s.remove(4) None >>> print s set([1, 2, 3, 6, 7, 8, 9]) >>> s.remove(0) KeyError: 0


.discard(x)

This operation also removes element  from the set.
If element  does not exist, it does not raise a KeyError.
The .discard(x) operation returns None.

Example>>> s = set([1, 2, 3, 4, 5, 6, 7, 8, 9]) >>> s.discard(5) >>> print s set([1, 2, 3, 4, 6, 7, 8, 9]) >>> print s.discard(4) None >>> print s set([1, 2, 3, 6, 7, 8, 9]) >>> s.discard(0) >>> print s set([1, 2, 3, 6, 7, 8, 9])


.pop()

This operation removes and return an arbitrary element from the set.
If there are no elements to remove, it raises a KeyError.

Example>>> s = set([1]) >>> print s.pop() 1 >>> print s set([]) >>> print s.pop() KeyError: pop from an empty set


Task

You have a non-empty set , and you have to execute  commands given in  lines.

The commands will be pop, remove and discard.

Input Format

The first line contains integer , the number of elements in the set .
The second line contains  space separated elements of set . All of the elements are non-negative integers, less than or equal to 9.
The third line contains integer , the number of commands.
The next  lines contains either pop, remove and/or discard commands followed by their associated value.

Constraints


Output Format

Print the sum of the elements of set  on a single line.

Sample Input

9
1 2 3 4 5 6 7 8 9
10
pop
remove 9
discard 9
discard 8
remove 7
pop 
discard 6
remove 5
pop 
discard 5

Sample Output

4

Explanation

After completing these  operations on the set, we get set([4]). Hence, the sum is .

Note: Convert the elements of set s to integers while you are assigning them. To ensure the proper input of the set, we have added the first two lines of code to the editor.

Solution in Python

n = int(input())
s = set(map(int, input().split()))
d = {"pop":s.pop, "remove":s.remove, "discard": s.discard}
for _ in range(int(input())):
    c = input().split()
    d[c[0]](int(c[1])) if len(c)>1 else d[c[0]]()
print(sum(s))

Explanation

What I actually did is bind those 3 words to their respective functions for the list s and then store it in a dictionary.

Now these values will become equal

>>> d["pop"]==s.pop
True
>>> d["remove"]==s.remove
True
>>> d["discard"]==s.discard
True

If a user enters

remove 5

Both of the following will perform our desired action

d["remove"](int("5"))
s.remove(5)

So we take input from the user and perform the action using d instead of s

>>> c = input().split()
["remove", "5"]
>>> c[0] == "remove"
True
>>> c[1] == "5
True

When c[1] is blank len of c will be 1 in such case we call our function without any parameter. Hence our code can be written like this

d[c[0]](int(c[1])) if len(c)>1 else d[c[0]]()

Or this

if len(c)>1:
	d[c[0]](int(c[1])) 
else:
	d[c[0]]()

And that's it! Hope it helped you understand clearly.