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lc911. online election

admin 11月 13, 2020 0

Description

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.

####TLE solution:

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class  {
  vector<vector<int>> votes;
  vector<int> spersons;
  vector<int> stimes;
    bool compPosition(int cur, int com, int start){
        for(int i = start; i >= 0; i--){
            if(spersons[i] == cur)
                return false;
            if(spersons[i] == com)
                return true;
        }
        return false;
    }
public:
    TopVotedCandidate(vector<int> persons, vector<int> times) {
        int size = times.size();
        stimes = times;
        spersons = persons;
        votes = vector<vector<int>>(size, vector<int>(size, 0));
        vector<int> allVotes(size, 0);
        for(int i = 0; i < persons.size(); i++){
            allVotes[persons[i]]++;
            votes[i] = allVotes;
        }    
    }

    int q(int t) {
        auto ind = lower_bound(stimes.begin(), stimes.end(), t);
        int curInd = (stimes[ind - stimes.begin()] == t) ? (ind - stimes.begin()) : (ind - stimes.begin() - 1 >= 0 ? ind - stimes.begin() - 1 : 0);
        
        vector<int> curVotes = votes[curInd];
        // for(int v : curVotes)
        //     cout << v << " ";
        // cout << endl;
        int maxV = 0;
        int res = 0;
        for(int i = curVotes.size()-1; i >= 0; i--){
            if(curVotes[i] > maxV){
                maxV = curVotes[i];
                res = i;
            } else if(curVotes[i] == maxV && compPosition(res, i, curInd)){
                res = i;
            }
        }
        return res;
    }
};

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

Best solution

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class  {
    map<int, int> timePeople;
public:
    TopVotedCandidate(vector<int> persons, vector<int> times) {
        int size = times.size();
        for(int i = 0; i < size; i++){
            timePeople[times[i]] = persons[i];
        }
        unordered_map<int, int> peopleVotes;
        int top = -1;
        for(auto it = timePeople.begin(); it != timePeople.end(); it++){
            peopleVotes[it->second]++;
            if(peopleVotes[it->second] >= peopleVotes[top])
                top = it->second;
            timePeople[it->first] = top;
        }
    }

    int q(int t) {
        return (--timePeople.upper_bound(t))->second;
    }
};

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