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

Given an array of names of candidates in an election. A candidate name in array represents a vote casted to the candidate. Print the name of candidates received Max vote. If there is tie, print lexicographically smaller name.

Examples:

Input :  votes[] = {"john", "johnny", "jackie", 
                    "johnny", "john", "jackie", 
                    "jamie", "jamie", "john",
                    "johnny", "jamie", "johnny", 
                    "john"};
Output : John
We have four Candidates with name as 'John', 
'Johnny', 'jamie', 'jackie'. The candidates
John and Johny get maximum votes. Since John
is alphabetically smaller, we print it.

Recommended: Please solve it on PRACTICE first, before moving on to the solution.

A simple solution is to run two loops and count occurrences of every word. Time complexity of this solution is O(n * n * MAX_WORD_LEN).

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

CPP

// 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 
        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); 
    } 
} 

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 

Output:

John

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 contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

My Personal Notes

Recommended: Please solve it on PRACTICE first, before moving on to the solution.

CPP

Java

C#

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