Subdomain Visit Count - LeetCode

Subdomain Visit Count is a problem that asks you to count the number of visits to different subdomains of a website. For example, if the website is ‘example.com’, the subdomains could be ‘a.example.com’, ‘b.example.com’, etc. The goal is to count the number of unique visits to each subdomain.
To solve this problem, we can use a dictionary to store the count of visits for each subdomain. We can iterate through the list of visited URLs and extract the subdomain using string manipulation techniques. Then, we can update the count for that subdomain in the dictionary.
Here’s a Python code example that solves the Subdomain Visit Count problem:

def subdomain_visit_count(URLs):
subdomain_count = {}
for url in URLs:
subdomain = get_subdomain(url)
if subdomain in subdomain_count:
subdomain_count[subdomain] += 1
else:
subdomain_count[subdomain] = 1
return subdomain_count
def get_subdomain(url):
parts = url.split('.')
if len(parts) < 3:
return ''
return '.'.join(parts[:-2])

Explanation:
The subdomain_visit_count function takes a list of URLs as input and returns a dictionary that maps subdomains to their visit counts. The get_subdomain function is a helper function that extracts the subdomain from a URL by splitting it on the dot (‘.’) and joining the parts before the last two segments.
In the subdomain_visit_count function, we iterate through each URL in the input list. For each URL, we extract the subdomain using the get_subdomain function and check if it exists in the subdomain_count dictionary. If it does, we increment its count by 1. If it doesn’t exist, we add it to the dictionary with a count of 1.
Finally, we return the subdomain_count dictionary containing the visit counts for each subdomain.
Now let’s see how we can optimize this solution and approach similar problems in the future.
Optimization:
To optimize our solution, we can use a collections.Counter instead of a dictionary to count the visits. The Counter class provides an efficient way to count the occurrences of each subdomain without explicitly checking for existence before incrementing the count. Here’s an optimized version of the code:

from collections import Counter
def subdomain_visit_count(URLs):
subdomain_count = Counter()
for url in URLs:
subdomain = get_subdomain(url)
subdomain_count[subdomain] += 1
return dict(subdomain_count)

In this optimized version, we import the Counter class from the collections module and use it to initialize the subdomain_count variable. We then iterate through each URL, extract the subdomain, and update its count in the Counter object using the [] operator. Finally, we convert the Counter object to a dictionary using the dict() constructor and return it as the result.
Similar Problems:
The Subdomain Visit Count problem is related to string manipulation and counting problems. Other similar problems you may encounter on LeetCode or in practice include:

1. IP Address Visit Count: Instead of URLs, you are given a list of IP addresses and need to count the number of unique visits to each IP address range (e.g., 192.168.1.0/24). You can use subnetting knowledge and string manipulation techniques to extract the relevant information from IP addresses.
2. Domain Visit Count: Similar to Subdomain Visit Count, but instead of subdomains, you need to count the number of visits to different top-level domains (e.g., .com, .net). You can extract the top-level domain using string manipulation techniques similar to extracting subdomains.
3. URL Parameter Visit Count: In this problem, you are given a list of URLs with parameters (e.g., example.com/page?id=123). You need to count the number of