LeetCode in Kotlin

911. Online Election

Medium

You are given two integer arrays persons and times. In an election, the ith 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.

Solution

class TopVotedCandidate(persons: IntArray, private val times: IntArray) {
    private val winnersAtTimeT: IntArray = IntArray(times.size)

    init {
        val counterArray = IntArray(persons.size)
        var maxVote = 0
        var maxVotedPerson = 0
        for (i in persons.indices) {
            val person = persons[i]
            val voteCount = counterArray[person]
            if (voteCount + 1 >= maxVote) {
                maxVote = voteCount + 1
                maxVotedPerson = person
            }
            winnersAtTimeT[i] = maxVotedPerson
            counterArray[persons[i]] = voteCount + 1
        }
    }

    fun q(t: Int): Int {
        var lo = 0
        var hi = times.size - 1
        if (t >= times[hi]) {
            lo = hi
        } else {
            while (lo < hi - 1) {
                val 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:
 * var obj = TopVotedCandidate(persons, times)
 * var param_1 = obj.q(t)
 */

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