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0911. Online Election.md

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0911. Online Election, medium, , freq: 17%, acceptance: 47.6%

In an election, the i-th vote was cast for persons[i] at time times[i].

Now, we would like to implement the following query function: TopVotedCandidate.q(int t) will return the number of 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.

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: At time 3, the votes are [0], and 0 is leading. At time 12, the votes are [0,1,1], and 1 is leading. At time 25, the votes are [0,1,1,0,0,1], and 1 is leading (as ties go to the most recent vote.) This continues for 3 more queries at time 15, 24, and 8.

Note:

1 <= persons.length = times.length <= 5000 0 <= persons[i] <= persons.length times is a strictly increasing array with all elements in [0, 10^9]. TopVotedCandidate.q is called at most 10000 times per test case. TopVotedCandidate.q(int t) is always called with t >= times[0].

// 320ms, 95%
class TopVotedCandidate {
    vector<int> votes;
    map<int,int> maxVotes;
public:
    TopVotedCandidate(vector<int>& persons, vector<int>& times) {
        votes.resize(persons.size()+1, 0);
        int maxV = 0, maxP = -1;
        for (int i = 0; i < persons.size(); i++) {
            auto pi = persons[i];
            votes[pi]++;
            if (votes[pi] >= maxV) {
                maxV = votes[pi];
                maxP = pi;
                maxVotes[times[i]] = maxP;
            }
        }
    }
    
    int q(int t) {
        if (maxVotes.empty())
            return 0;
        auto it = maxVotes.lower_bound(t);
        if (it == maxVotes.end() ||
           it->first > t) {
            if (it != maxVotes.begin())
                --it;
        }
        return it->second;
    }
};

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