HackerRank Python: collections.Counter() Solution

Table of Contents

Question

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]

Task

Raghu is a shoe shop owner. His shop has X number of shoes.

He has a list containing the size of each shoe he has in his shop.

There are N number of customers who are willing to pay xi amount of money only if they get the shoe of their desired size.

Your task is to compute how much money Raghu earned.

Input Format

The first line contains X, the number of shoes.

The second line contains the space separated list of all the shoe sizes in the shop.

The third line contains N, the number of customers.

The next N lines contain the space separated values of the shoe size desired by the customer and xi, the price of the shoe.

Constraints

0 < X < 10^3
0 < N <= 10^3
20 < xi < 100
2 < shoe size < 20

Output Form

Output Format

Print the amount of money earned by Raghu.

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

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 = 55 + 45 + 40 + 60 = $200

Solution

				
					from collections import Counter

# Input
X = int(input())  # Number of shoes
shoe_sizes = list(map(int, input().split()))  # List of shoe sizes
N = int(input())  # Number of customers

# Count the occurrences of each shoe size
shoe_inventory = Counter(shoe_sizes)

# Calculate the total money earned
total_earnings = 0
for _ in range(N):
    size, price = map(int, input().split())
    if shoe_inventory[size] > 0:  # If the requested shoe size is available
        total_earnings += price
        shoe_inventory[size] -= 1  # Decrease the count of that shoe size

# Output
print(total_earnings)

Explanation

We start by importing the Counter class from the collections module. This class is used to count the occurrences of elements in a list efficiently.
The first part of the code handles the input. We read the following values from the input:
- X: The number of shoes in the shop.
- shoe_sizes: A list of shoe sizes in the shop.
- N: The number of customers.
- For each customer, we read their requested size and the price they are willing to pay.
Next, we create a Counter object called shoe_inventory from the shoe_sizes list. This will count the occurrences of each shoe size in the inventory.
We initialize a variable total_earnings to keep track of the total money earned by Raghu. Initially, it is set to 0.
We then iterate N times, once for each customer. Inside the loop, we do the following:
- Read the size and price requested by the customer.
- Check if the requested size is available in the shoe_inventory by checking if its count is greater than 0.
- If the requested size is available, we add the price to total_earnings and decrement the count of that shoe size in shoe_inventory by 1.
Finally, we print the value of total_earnings, which represents the amount of money earned by Raghu.