# 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
}
}

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)
*/