Hackerrank Collections Counter Solution

collections.Counter()
A counter is a container that stores elements as dictionary keys, and their counts are stored as dictionary values.

_{Sample Code}

>>> from collections import Counter
>>> 
>>> myList = [1,1,2,3,4,5,3,2,3,4,2,1,2,3]
>>> print Counter(myList)
Counter({2: 4, 3: 4, 1: 3, 4: 2, 5: 1})
>>>
>>> print Counter(myList).items()
[(1, 3), (2, 4), (3, 4), (4, 2), (5, 1)]
>>> 
>>> print Counter(myList).keys()
[1, 2, 3, 4, 5]
>>> 
>>> print Counter(myList).values()
[3, 4, 4, 2, 1]

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Task

is a shoe shop owner. His shop has  number of shoes.
He has a list containing the size of each shoe he has in his shop.
There are  number of customers who are willing to pay  amount of money only if they get the shoe of their desired size.

Your task is to compute how much money  earned.

Input Format

The first line contains , the number of shoes.
The second line contains the space separated list of all the shoe sizes in the shop.
The third line contains , the number of customers.
The next  lines contain the space separated values of the  desired by the customer and , the price of the shoe.

Constraints

Output Format

Print the amount of money earned by .

Sample Input

10
2 3 4 5 6 8 7 6 5 18
6
6 55
6 45
6 55
4 40
18 60
10 50

Sample Output

200

Explanation

Customer 1: Purchased size 6 shoe for $55.
Customer 2: Purchased size 6 shoe for $45.
Customer 3: Size 6 no longer available, so no purchase.
Customer 4: Purchased size 4 shoe for $40.
Customer 5: Purchased size 18 shoe for $60.
Customer 6: Size 10 not available, so no purchase.

Total money earned = $200

Solution in Python

from collections import Counter

int(input())
sizes = list(map(int,input().split()))
money = 0
stock = Counter(sizes)
for i in range(int(input())):
    x,y = list(map(int,input().split()))
    if stock[x]:
        money+=y
        stock[x]-=1
print(money)
    

Explanation

We use the Counter function to count the number of pair of shoes for each size we have

>>> Counter([2, 3, 4, 5, 6, 8, 7, 6, 5, 18])
Counter({2: 1, 3: 1, 4: 1, 5: 2, 6: 2, 8: 1, 7: 1, 18: 1})

Then we decrement the count of each pair and increment the value of our variable money for every sale made.

If the stock count of the desired pair by a customer is 0 then we just continue to the next loop(or customer)