LeetCode 1355: Activity Participants Solution

Master LeetCode problem 1355 (Activity Participants), 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.

1355. Activity Participants

Medium

Database

Problem Explanation

Explanation:

To solve this problem, we need to find the list of participants who attended at least one activity. We can achieve this by iterating through the activities and maintaining a set of unique participants.

We will iterate through the activities list and add each participant to a set.
After iterating through all activities, we will have a set of unique participants who attended at least one activity.
Finally, we will convert the set back to a list and return it as the result.

Time Complexity:

The time complexity of this approach is O(n), where n is the total number of participants across all activities.

Space Complexity:

The space complexity of this approach is also O(n), where n is the total number of participants across all activities.

: :

Solution Code

import java.util.*;

class Solution {
    public List<String> mostActive(List<String> activities) {
        Set<String> participants = new HashSet<>();
        for (String activity : activities) {
            participants.add(activity);
        }
        return new ArrayList<>(participants);
    }
}

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