Find the Most Popular Element in Int[] Array

Find the most popular element in int[] array

public int getPopularElement(int[] a)
{
  int count = 1, tempCount;
  int popular = a[0];
  int temp = 0;
  for (int i = 0; i < (a.length - 1); i++)
  {
    temp = a[i];
    tempCount = 0;
    for (int j = 1; j < a.length; j++)
    {
      if (temp == a[j])
        tempCount++;
    }
    if (tempCount > count)
    {
      popular = temp;
      count = tempCount;
    }
  }
  return popular;
}

Finding frequency of most frequent element inside an array

public static int numberOfMatches(int[] numbers) {
    int mostMatches = 0;

    for(int i = 0; i < numbers.length; i++) {
        int matches = 0;
        int holder = numbers[i];

        for(int number : numbers) {
            if(number == holder) {
                matches++;
            }
        }

        if(matches > mostMatches)
            mostMatches = matches;
    }
    return mostMatches;
}

This accepts an array. It checks the length of the array, and loops for each slot.
For each slot, I create 2 variables. holder grabs the value in the slot, and we increase matches any time there is a match.

Once all possible matches have been found for that slot, it compares the amount of matches found to the highest amount of matches found so far.

Most frequent number in array in Java

One of the solution is to create the Map with Integer as a key and Integer as the value. You will have to iterate through the array and increase the amount of the numbers in a map.

Integer[] arr = {4, 1, 4, 1, 3};
Map<Integer,Integer> integersCount = new HashMap<Integer,Integer>();

for (Integer i : arr){
    if (!integersCount.containsKey(i))
        integersCount.put(i, 1);
    else
        integersCount.put(i, integersCount.get(i) + 1);
    }

After that you can go through the map and remember the position of the element which has the greatest value.

For another solution I recommend counting the numbers in another array - read about "counting sort".

Determine the most common occurrence in an array

Using a Map<Integer, Integer> should be simple as:

int mostFrequent(int... ary) {
    Map<Integer, Integer> m = new HashMap<Integer, Integer>();

    for (int a : ary) {
        Integer freq = m.get(a);
        m.put(a, (freq == null) ? 1 : freq + 1);
    }

    int max = -1;
    int mostFrequent = -1;

    for (Map.Entry<Integer, Integer> e : m.entrySet()) {
        if (e.getValue() > max) {
            mostFrequent = e.getKey();
            max = e.getValue();
        }
    }

    return mostFrequent;
}

find largest most frequent element

Step1: QuickSort on ArrayList<Integer> arr;

Step2: Iteration on ArrayList<Integer> arr as you have done.

---

Related Topics