LeetCode 1364: Number of Trusted Contacts of a Customer Solution

Master LeetCode problem 1364 (Number of Trusted Contacts of a Customer), 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.

1364. Number of Trusted Contacts of a Customer

Medium

Database

Problem Explanation

Explanation

To solve this problem, we can use a hashmap to store the trusted contacts of each customer. We iterate through the list of customers and their trusted contacts, updating the hashmap accordingly. Then, we iterate through the hashmap to count the number of trusted contacts for each customer.

Solution Code

import java.util.*;

class Solution {
    public List<Integer> numOfTrustedContacts(List<List<Integer>> contacts) {
        Map<Integer, Set<Integer>> trustedContacts = new HashMap<>();
        
        for (List<Integer> contact : contacts) {
            int customer = contact.get(0);
            int trustedContact = contact.get(1);
            
            trustedContacts.putIfAbsent(customer, new HashSet<>());
            trustedContacts.get(customer).add(trustedContact);
        }
        
        List<Integer> result = new ArrayList<>();
        for (int customer : trustedContacts.keySet()) {
            int count = 0;
            for (Set<Integer> contactsSet : trustedContacts.values()) {
                if (contactsSet.contains(customer)) {
                    count++;
                }
            }
            result.add(count);
        }
        
        return result;
    }
}

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