Write a mode method in Java to find the most frequently occurring element in an array

Question

The question goes:

Write a method called mode that returns the most frequently occurring element of an array of integers. Assume that the array has at le

Answer 1

This is not the most fastest method around the block, but is fairly simple to understand if you don't wanna involve yourself in HashMaps and also want to avoid using 2 for loops for complexity issues....

    int mode(int n, int[] ar) {
    int personalMax=1,totalMax=0,maxNum=0;

    for(int i=0;i<n-1;i++)
    {

        if(ar[i]==ar[i+1])
        {
            personalMax++;

            if(totalMax<personalMax)
            {
                totalMax=personalMax;
                maxNum=ar[i];
            }
        }    
        else
        {
            personalMax=1;
        }
    }
    return maxNum;
}

Answer 2

public int mode(int[] array) {
    int mode = array[0];
    int maxCount = 0;
    for (int i = 0; i < array.length; i++) {
        int value = array[i];
        int count = 1;
        for (int j = 0; j < array.length; j++) {
            if (array[j] == value) count++;
            if (count > maxCount) {
                mode = value;
                maxCount = count;
            }
        }
    }
    return mode;
}

Answer 3

Based on the answer from @codemania23 and the Java Docs for HashMap I wrote this code snipped and tests of a method that returns the most occurrent number in an array of numbers.

import java.util.HashMap;

public class Example {

    public int mostOcurrentNumber(int[] array) {
        HashMap<Integer, Integer> map = new HashMap<>();
        int result = -1, max = 1;
        for (int arrayItem : array) {
            if (map.putIfAbsent(arrayItem, 1) != null) {
                int count = map.get(arrayItem) + 1;
                map.put(arrayItem, count);
                if (count > max) {
                    max = count;
                    result = arrayItem;
                }
            }
        }

        return result;
    }
}

Unit Tests

import org.junit.Test;

import static junit.framework.Assert.assertEquals;

public class ExampleTest extends Example {

    @Test
    public void returnMinusOneWhenInputArrayIsEmpty() throws Exception {
        int[] array = new int[0];
        assertEquals(mostOcurrentNumber(array), -1);
    }

    @Test
    public void returnMinusOneWhenElementsUnique() {
        int[] array = new int[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
        assertEquals(-1, mostOcurrentNumber(array));
    }

    @Test
    public void returnOne() throws Exception {
        int[] array = new int[]{0, 1, 0, 0, 1, 1, 1};
        assertEquals(1, mostOcurrentNumber(array));
    }

    @Test
    public void returnFirstMostOcurrentNumber() throws Exception {
        int[] array = new int[]{0, 1, 0, 1, 0, 0, 1, 1};
        assertEquals(0, mostOcurrentNumber(array));
    }
}

Answer 4

check this.. Brief:Pick each element of array and compare it with all elements of the array, weather it is equal to the picked on or not.

  int popularity1 = 0;
  int popularity2 = 0;
  int popularity_item, array_item; //Array contains integer value. Make it String if array contains string value.
  for(int i =0;i<array.length;i++){
      array_item = array[i];
      for(int j =0;j<array.length;j++){
          if(array_item == array[j])
             popularity1 ++;
          {
      if(popularity1 >= popularity2){
          popularity_item = array_item;
          popularity2 = popularity1;
      }
      popularity1 = 0;
  }
  //"popularity_item" contains the most repeted item in an array.

Answer 5

THIS CODE CALCULATES MODE, MEDIAN, AND MEAN. IT IS TESTED AND IT DOES WORK. It is a complete program from start to finish and will compile.

import java.util.Arrays;
import java.util.Random;
import java.math.*;
/**
 *
 * @author Mason
 */
public class MODE{

    public static void main(String args[])
    {
        System.out.print("Enter the quantity of random numbers  ===>>  ");
        int listSize = Expo.enterInt();
        System.out.println();
        ArrayStats intStats = new ArrayStats(listSize);
        intStats.randomize();
        intStats.computeMean();
        intStats.computeMedian();
        intStats.computeMode();
        intStats.displayStats();
        System.out.println();
    }
}


class ArrayStats
{

    private int list[];
    private int size;
    private double mean;        
    private double median;      
    private int mode;           

    public ArrayStats(int s)//initializes class object
    {
        size = s;
        list = new int[size];
    }

    public void randomize()
    {
        //This will provide same numbers every time... If you want to randomize this, you can
        Random rand = new Random(555);
        for (int k = 0; k < size; k++)
            list[k] = rand.nextInt(11) + 10;  
    }

    public void computeMean()
    {
               double accumulator=0;
               for (int index=0;index<size;index++)
               accumulator+= list[index];

               mean = accumulator/size;
    }

        public void computeMedian()
{
        Arrays.sort(list);
                if((size%2!=0))
                    median = list[((size-1)/2)];
                else if(size!=1&&size%2==0)
                {
                    double a =(size)/2-0.5;
                    int a2 =  (int)Math.ceil(a);
                    double b =(size)/2-0.5;
                    int b2 = (int)Math.floor(b);
                    median = (double)(list[a2]+list[b2])/2;
                }
                else if (size ==1)
                    median = list[0];
        }

    public void computeMode()
    {
 int popularity1 = 0;
  int popularity2 = 0;
  int array_item; //Array contains integer value. Make it String if array contains string value.
  for(int i =0;i<list.length;i++){
      array_item = list[i];
      for(int j =0;j<list.length;j++){
          if(array_item == list[j])
             popularity1 ++;
      }
      if(popularity1 >= popularity2){
          mode = array_item;
          popularity2 = popularity1;
      }


      popularity1 = 0;
  }}

    public void displayStats()
    {
        System.out.println(Arrays.toString(list));
        System.out.println();
        System.out.println("Mean: " + mean);
        System.out.println("Median: " + median);
        System.out.println("Mode: " + mode);
        System.out.println();
    }

}

Answer 6

    Arrays.sort(arr);
    int max=0,mode=0,count=0;
    for(int i=0;i<N;i=i+count) {
        count = 1;
        for(int j=i+1; j<N; j++) {
            if(arr[i] == arr[j])
                count++;
        }
        if(count>max) {
            max=count;
            mode = arr[i];
        }
    }