Subdomain Visit Count

Problem Description

Given an array of count-paired domains, return an array of the count-paired domains of each subdomain in the input. A count-paired domain is in the format "rep d1.d2.d3" or "rep d1.d2", where "rep" is the number of visits to the domain, and "d1.d2.d3" is the domain itself.

Key Insights

• Each domain visit also counts for its parent domains.
• We need to derive visits for all levels of subdomains.
• A hash map can efficiently store and accumulate visit counts for each subdomain.

Space and Time Complexity

Time Complexity: O(N * M), where N is the number of count-paired domains and M is the maximum number of subdomains derived from a single count-paired domain. Space Complexity: O(S), where S is the number of unique subdomains.

Solution

To solve this problem, we can use a hash map (or dictionary) to store the total visit counts for each subdomain. For each count-paired domain in the input, we will:

1. Split the string into the number of visits (rep) and the domain.
2. Split the domain into its components (subdomains).
3. For each component, we will build the full subdomain from the current component to the top-level domain, accumulating the visit counts in the hash map.
4. Finally, we will format the results from the hash map back into the required output format.

Code Solutions