Find winner of an election where votes are represented as candidate names

Given an array of names of candidates in an election. A candidate’s name in the array represents a vote cast on the candidate. Print the name of candidates who received the maximum vote. If there is a tie, print a lexicographically smaller name.

Examples: 

Input:  votes[] = {“john”, “johnny”, “jackie”, “johnny”, “john”, “jackie”, “jamie”, “jamie”, “john”, “johnny”, “jamie”, “johnny”, “john”} 
Output: John
Explanation: We have four Candidates with name as ‘John’, ‘Johnny’, ‘jamie’, ‘jackie’. The candidates John and Johny get maximum votes. Since John is alphabetically smaller.

Input: votes[] = {“virat”, “rohit”, “rishabh”, “rohit”, “virat”, “rohit”}
Output: rohit
Explanation: We have three Candidates with name as ‘virat’, ‘rohit’, ‘rishabh’. rohit get maximum votes. 

Naive Approach:

A simple solution is to run two loops and count the occurrences of every word. And then find the maximum count.  

Time Complexity: O(n * n * MAX_WORD_LEN).
Auxiliary Space: O(1) 

Find winner of an election where votes are represented as candidate names using Hashing:

An efficient solution is to use Hashing. Insert all votes in a hash map and keep track of counts of different names. Finally, traverse the map and print the person with the maximum votes.

Follow the steps below to solve the problem:

• Create a map of string, value pair
• Now iterate on the votes array and increment the count of every string
• Traverse the map and the string having maximum count store it as a string variable
• If there is a tie pick the smaller one

Below is the Implementation of the above approach:

C++

// C++++ program to find winner in an election.
#include "bits/stdc++.h"
using namespace std;

/* We have four Candidates with name as 'John',
  'Johnny', 'jamie', 'jackie'.
   The votes in String array are as per the
   votes casted. Print the name of candidates
   received Max vote. */
void findWinner(vector<string>& votes)
{

    // Insert all votes in a hashmap
    unordered_map<string, int> mapObj;
    for (auto& str : votes) {
        mapObj[str]++;
    }

    // Traverse through map to find the candidate
    // with maximum votes.
    int maxValueInMap = 0;
    string winner;
    for (auto& entry : mapObj) {
        string key = entry.first;
        int val = entry.second;
        if (val > maxValueInMap) {
            maxValueInMap = val;
            winner = key;
        }

        // If there is a tie, pick lexicographically
        // smaller.
        else if (val == maxValueInMap && winner > key)
            winner = key;
    }
    cout << winner << endl;
}

// Driver code
int main()
{
    vector<string> votes
        = { "john", "johnny", "jackie", "johnny",
            "john", "jackie", "jamie",  "jamie",
            "john", "johnny", "jamie",  "johnny",
            "john" };

    findWinner(votes);
    return 0;
}

Java

// Java program to find winner in an election.
import java.util.*;

public class ElectoralVotingBallot {
    /* We have four Candidates with name as 'John',
      'Johnny', 'jamie', 'jackie'.
       The votes in String array are as per the
       votes casted. Print the name of candidates
       received Max vote. */
    public static void findWinner(String votes[])
    {
        // Insert all votes in a hashmap
        Map<String, Integer> map
            = new HashMap<String, Integer>();
        for (String str : votes) {
            if (map.keySet().contains(str))
                map.put(str, map.get(str) + 1);
            else
                map.put(str, 1);
        }

        // Traverse through map to find the candidate
        // with maximum votes.
        int maxValueInMap = 0;
        String winner = "";
        for (Map.Entry<String, Integer> entry :
             map.entrySet()) {
            String key = entry.getKey();
            Integer val = entry.getValue();
            if (val > maxValueInMap) {
                maxValueInMap = val;
                winner = key;
            }

            // If there is a tie, pick lexicographically
            // smaller.
            else if (val == maxValueInMap
                     && winner.compareTo(key) > 0)
                winner = key;
        }
        System.out.println(winner);
    }

    // Driver code
    public static void main(String[] args)
    {
        String[] votes
            = { "john", "johnny", "jackie", "johnny",
                "john", "jackie", "jamie",  "jamie",
                "john", "johnny", "jamie",  "johnny",
                "john" };

        findWinner(votes);
    }
}

Python3

# Python3 program to find winner in an election.
from collections import defaultdict

''' We have four Candidates with name as 'John',
'Johnny', 'jamie', 'jackie'.
The votes in String array are as per the
votes casted. Print the name of candidates
received Max vote. '''


def findWinner(votes):

    # Insert all votes in a hashmap
    mapObj = defaultdict(int)

    for st in votes:
        mapObj[st] += 1

    # Traverse through map to find the
    # candidate with maximum votes.
    maxValueInMap = 0
    winner = ""

    for entry in mapObj:
        key = entry
        val = mapObj[entry]

        if (val > maxValueInMap):
            maxValueInMap = val
            winner = key

        # If there is a tie, pick lexicographically
        # smaller.
        else if (val == maxValueInMap and
                 winner > key):
            winner = key

    print(winner)


# Driver code
if __name__ == "__main__":

    votes = ["john", "johnny", "jackie",
             "johnny", "john", "jackie",
             "jamie", "jamie", "john",
             "johnny", "jamie", "johnny",
             "john"]

    findWinner(votes)

# This code is contributed by ukasp

C#

// C# program to find winner in an election.
using System;
using System.Collections.Generic;

public class ElectoralVotingBallot {
    /* We have four Candidates with name as 'John',
    'Johnny', 'jamie', 'jackie'.
    The votes in String array are as per the
    votes casted. Print the name of candidates
    received Max vote. */
    public static void findWinner(String[] votes)
    {
        // Insert all votes in a hashmap
        Dictionary<String, int> map
            = new Dictionary<String, int>();
        foreach(String str in votes)
        {
            if (map.ContainsKey(str))
                map[str] = map[str] + 1;
            else
                map.Add(str, 1);
        }

        // Traverse through map to find the candidate
        // with maximum votes.
        int maxValueInMap = 0;
        String winner = "";
        foreach(KeyValuePair<String, int> entry in map)
        {
            String key = entry.Key;
            int val = entry.Value;
            if (val > maxValueInMap) {
                maxValueInMap = val;
                winner = key;
            }

            // If there is a tie, pick lexicographically
            // smaller.
            else if (val == maxValueInMap
                     && winner.CompareTo(key) > 0)
                winner = key;
        }
        Console.WriteLine(winner);
    }

    // Driver code
    public static void Main(String[] args)
    {
        String[] votes
            = { "john", "johnny", "jackie", "johnny",
                "john", "jackie", "jamie",  "jamie",
                "john", "johnny", "jamie",  "johnny",
                "john" };

        findWinner(votes);
    }
}

// This code is contributed by PrinciRaj1992

Javascript

<script>
// Javascript program to find winner in an election.

    /* We have four Candidates with name as 'John',
      'Johnny', 'jamie', 'jackie'.
       The votes in String array are as per the
       votes casted. Print the name of candidates
       received Max vote. */
    function findWinner(votes)
    {
        let map = new Map();
        for(let i=0;i<votes.length;i++)
        {
            if(map.has(votes[i]))
            {
                map.set(votes[i], map.get(votes[i]) + 1);
            }

            else
                map.set(votes[i], 1);
        }

        // Traverse through map to find the candidate
        // with maximum votes.
        let maxValueInMap = 0;
        let winner = "";
        for (let [key, value] of map.entries())
        {
            let Key  = key;
            let val = value;
            if (val > maxValueInMap)
            {
                maxValueInMap = val;
                winner = key;
            }

            // If there is a tie, pick lexicographically
            // smaller.
            else if (val == maxValueInMap &&
                winner>Key)
                winner = Key;
        }
        document.write(winner);

    }

    // Driver code
    let votes=["john", "johnny", "jackie",
                         "johnny", "john", "jackie",
                         "jamie", "jamie", "john",
                         "johnny", "jamie", "johnny",
                         "john"];
    findWinner(votes);
    // This code is contributed by rag2127
</script>

Output

john

Time Complexity: O(N), where N is the total number of votes.
Auxiliary Space: O(N), since unordered_map data structure is used.

Another efficient solution is to use Trie. Please refer most frequent word in an array of strings.

This article is contributed by Ishfaq Ramzan Nagoo. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.