LeetCode 911: Online Election Solution

Master LeetCode problem 911 (Online Election), 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.

911. Online Election

Medium

Array Hash Table Binary Search Design

Problem Explanation

Explanation:

To solve this problem efficiently, we can use a HashMap to keep track of the number of votes each person has received at any given time. We will also maintain a TreeMap to store the total votes for each person at different times.

Constructor (TopVotedCandidate):
- Create a HashMap votesCount to store the number of votes received by each person.
- Create a TreeMap winners to store the total votes for each person at different times.
- Iterate through the persons and times arrays to update the votesCount and winners maps.
Query (q):
- Use the TreeMap floorEntry() method to find the entry with the largest time value less than or equal to the given time t.
- Return the person with the most votes at that time.

Solution Code

class TopVotedCandidate {
    Map<Integer, Integer> votesCount;
    TreeMap<Integer, Integer> winners;
    
    public TopVotedCandidate(int[] persons, int[] times) {
        votesCount = new HashMap<>();
        winners = new TreeMap<>();
        
        int maxVotes = 0;
        int currentWinner = -1;
        
        for (int i = 0; i < persons.length; i++) {
            votesCount.put(persons[i], votesCount.getOrDefault(persons[i], 0) + 1);
            int votes = votesCount.get(persons[i]);
            
            if (votes >= maxVotes) {
                maxVotes = votes;
                currentWinner = persons[i];
            }
            
            winners.put(times[i], currentWinner);
        }
    }
    
    public int q(int t) {
        int time = winners.floorKey(t);
        return winners.get(time);
    }
}

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