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911. Online Election

Description

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.

Solutions

Binary search.

  • class TopVotedCandidate {
    private int[] times;
    private int[] wins;

    public TopVotedCandidate(int[] persons, int[] times) {
        int n = persons.length;
        int mx = 0, cur = 0;
        this.times = times;
        wins = new int[n];
        int[] counter = new int[n];
        for (int i = 0; i < n; ++i) {
            int p = persons[i];
            if (++counter[p] >= mx) {
                mx = counter[p];
                cur = p;
            }
            wins[i] = cur;
        }
    }

    public int q(int t) {
        int left = 0, right = wins.length - 1;
        while (left < right) {
            int mid = (left + right + 1) >>> 1;
            if (times[mid] <= t) {
                left = mid;
            } else {
                right = mid - 1;
            }
        }
        return wins[left];
    }
}

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

  • class TopVotedCandidate {
public:
    vector<int> times;
    vector<int> wins;

    TopVotedCandidate(vector<int>& persons, vector<int>& times) {
        int n = persons.size();
        wins.resize(n);
        int mx = 0, cur = 0;
        this->times = times;
        vector<int> counter(n);
        for (int i = 0; i < n; ++i) {
            int p = persons[i];
            if (++counter[p] >= mx) {
                mx = counter[p];
                cur = p;
            }
            wins[i] = cur;
        }
    }

    int q(int t) {
        int left = 0, right = wins.size() - 1;
        while (left < right) {
            int mid = left + right + 1 >> 1;
            if (times[mid] <= t)
                left = mid;
            else
                right = mid - 1;
        }
        return wins[left];
    }
};

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

  • class TopVotedCandidate:
    def __init__(self, persons: List[int], times: List[int]):
        mx = cur = 0
        counter = Counter()
        self.times = times
        self.wins = []
        for i, p in enumerate(persons):
            counter[p] += 1
            if counter[p] >= mx:
                mx, cur = counter[p], p
            self.wins.append(cur)

    def q(self, t: int) -> int:
        left, right = 0, len(self.wins) - 1
        while left < right:
            mid = (left + right + 1) >> 1
            if self.times[mid] <= t:
                left = mid
            else:
                right = mid - 1
        return self.wins[left]


# Your TopVotedCandidate object will be instantiated and called as such:
# obj = TopVotedCandidate(persons, times)
# param_1 = obj.q(t)


  • type TopVotedCandidate struct {
	times []int
	wins  []int
}

func Constructor(persons []int, times []int) TopVotedCandidate {
	mx, cur, n := 0, 0, len(persons)
	counter := make([]int, n)
	wins := make([]int, n)
	for i, p := range persons {
		counter[p]++
		if counter[p] >= mx {
			mx = counter[p]
			cur = p
		}
		wins[i] = cur
	}
	return TopVotedCandidate{times, wins}
}

func (this *TopVotedCandidate) Q(t int) int {
	left, right := 0, len(this.wins)-1
	for left < right {
		mid := (left + right + 1) >> 1
		if this.times[mid] <= t {
			left = mid
		} else {
			right = mid - 1
		}
	}
	return this.wins[left]
}

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

  • class TopVotedCandidate {
    private times: number[];
    private wins: number[];

    constructor(persons: number[], times: number[]) {
        const n = persons.length;
        this.times = times;
        this.wins = new Array<number>(n).fill(0);
        const cnt: Array<number> = new Array<number>(n).fill(0);
        let cur = 0;
        for (let i = 0; i < n; ++i) {
            const p = persons[i];
            cnt[p]++;
            if (cnt[cur] <= cnt[p]) {
                cur = p;
            }
            this.wins[i] = cur;
        }
    }

    q(t: number): number {
        const search = (t: number): number => {
            let l = 0,
                r = this.times.length;
            while (l < r) {
                const mid = (l + r) >> 1;
                if (this.times[mid] > t) {
                    r = mid;
                } else {
                    l = mid + 1;
                }
            }
            return l;
        };
        const i = search(t) - 1;
        return this.wins[i];
    }
}

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

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