LeetCode 811: Subdomain Visit Count Solution

Master LeetCode problem 811 (Subdomain Visit Count), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

811. Subdomain Visit Count

Medium

Array Hash Table String Counting

Problem Explanation

Explanation

To solve this problem, we can iterate through each domain in the input array, split the count and domain parts, and then split the domain into its subdomains. We will maintain a hashmap to store the count of visits for each subdomain. By iterating through each domain and its subdomains, we can update the count for each subdomain in the hashmap. Finally, we will construct the result array by combining the count and subdomain.

Time complexity: O(n * m), where n is the number of domains and m is the maximum number of subdomains in a domain.
Space complexity: O(n * m), where n is the number of domains and m is the maximum number of subdomains in a domain.

Solution Code

import java.util.*;

class Solution {
    public List<String> subdomainVisits(String[] cpdomains) {
        Map<String, Integer> countMap = new HashMap<>();
        
        for (String cpdomain : cpdomains) {
            String[] parts = cpdomain.split(" ");
            int count = Integer.parseInt(parts[0]);
            String domain = parts[1];
            
            String[] subdomains = domain.split("\\.");
            StringBuilder sb = new StringBuilder();
            
            for (int i = subdomains.length - 1; i >= 0; i--) {
                sb.insert(0, subdomains[i]);
                countMap.put(sb.toString(), countMap.getOrDefault(sb.toString(), 0) + count);
                sb.insert(0, ".");
            }
        }
        
        List<String> result = new ArrayList<>();
        for (Map.Entry<String, Integer> entry : countMap.entrySet()) {
            result.add(entry.getValue() + " " + entry.getKey());
        }
        
        return result;
    }
}

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