g0901_1000.s0911_online_election.TopVotedCandidate Maven / Gradle / Ivy

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package g0901_1000.s0911_online_election;

// #Medium #Array #Hash_Table #Binary_Search #Design #Binary_Search_II_Day_20
// #2022_03_28_Time_63_ms_(98.81%)_Space_50.5_MB_(99.53%)

/**
 * 911 - Online Election\.
 *
 * Medium
 *
 * You are given two integer arrays `persons` and `times`. In an election, the i^th vote was cast for `persons[i]` at time `times[i]`.
 *
 * For each query at a time `t`, find the person that was leading the election at time `t`. Votes cast at time `t` will count towards our query. In the case of a tie, the most recent vote (among tied candidates) wins.
 *
 * Implement the `TopVotedCandidate` class:
 *
 * *   `TopVotedCandidate(int[] persons, int[] times)` Initializes the object with the `persons` and `times` arrays.
 * *   `int q(int t)` Returns the number of the person that was leading the election at time `t` according to the mentioned rules.
 *
 * **Example 1:**
 *
 * **Input** ["TopVotedCandidate", "q", "q", "q", "q", "q", "q"] [[[0, 1, 1, 0, 0, 1, 0], [0, 5, 10, 15, 20, 25, 30]], [3], [12], [25], [15], [24], [8]]
 *
 * **Output:** [null, 0, 1, 1, 0, 0, 1]
 *
 * **Explanation:** TopVotedCandidate topVotedCandidate = new TopVotedCandidate([0, 1, 1, 0, 0, 1, 0], [0, 5, 10, 15, 20, 25, 30]); topVotedCandidate.q(3); // return 0, At time 3, the votes are [0], and 0 is leading. topVotedCandidate.q(12); // return 1, At time 12, the votes are [0,1,1], and 1 is leading. topVotedCandidate.q(25); // return 1, At time 25, the votes are [0,1,1,0,0,1], and 1 is leading (as ties go to the most recent vote.) topVotedCandidate.q(15); // return 0 topVotedCandidate.q(24); // return 0 topVotedCandidate.q(8); // return 1
 *
 * **Constraints:**
 *
 * *   `1 <= persons.length <= 5000`
 * *   `times.length == persons.length`
 * *   `0 <= persons[i] < persons.length`
 * *   0 <= times[i] <= 10⁹
 * *   `times` is sorted in a strictly increasing order.
 * *   times[0] <= t <= 10⁹
 * *   At most 10⁴ calls will be made to `q`.
**/
public class TopVotedCandidate {
    private final int[] times;
    private final int[] winnersAtTimeT;

    public TopVotedCandidate(int[] persons, int[] times) {
        this.times = times;
        this.winnersAtTimeT = new int[times.length];
        int[] counterArray = new int[persons.length];
        int maxVote = 0;
        int maxVotedPerson = 0;
        for (int i = 0; i < persons.length; i++) {
            int person = persons[i];
            int voteCount = counterArray[person];
            if (voteCount + 1 >= maxVote) {
                maxVote = voteCount + 1;
                maxVotedPerson = person;
            }
            winnersAtTimeT[i] = maxVotedPerson;
            counterArray[persons[i]] = voteCount + 1;
        }
    }

    public int q(int t) {
        int lo = 0;
        int hi = times.length - 1;
        if (t >= times[hi]) {
            lo = hi;
        } else {
            while (lo < hi - 1) {
                int mid = lo + (hi - lo) / 2;
                if (times[mid] == t) {
                    lo = mid;
                    break;
                } else if (times[mid] > t) {
                    hi = mid;
                } else {
                    lo = mid;
                }
            }
        }
        return winnersAtTimeT[lo];
    }
}

/*
 * Your TopVotedCandidate object will be instantiated and called as such:
 * TopVotedCandidate obj = new TopVotedCandidate(persons, times);
 * int param_1 = obj.q(t);
 */