CODEWITHSUNDEEP
javaarrays
user12763537
user12763537

Reputation: 23

How to print out all elemets that is most frequent elemets in a array

I need to print out the numbers that are the most frequent elements in an array. Say that I have an int array like this:

int[] array = {1, 2, 3, 3, 3, 5}

I will then need to print out 3, as that is the most frequent element. But, I also need to print out the element that appear as frequent. Lets say I have this array now:

int[] array = {1, 2, 3, 3, 3, 5, 5, 5, 6, 7, 7, 7}

I then need to print out (ordered) 3, 5 and 7, as all three off them are the most frequent elements together. So the output needs to look like this: 

3
5
7

This is the code I have so far (it works for printing out only one off the most frequent numbers)

   Arrays.sort(diceSumArray);

    int maxCount = 1;
    int index = 1;

    int r = diceSumArray[0];

    for (int i = 1; i < diceSumArray.length; i++) {
        if (diceSumArray[i] == diceSumArray[i-1]) {
            index++;
        } else {
            if (index > maxCount) {
                maxCount = index;
                r = diceSumArray[i-1];
            }
            index = 1;
        }
    }

    // not sure where to put the print or if the code below is necessary 
    System.out.println(r);

    if (index > maxCount) {
        maxCount = index;
        r = diceSumArray[diceSumArray.length -1];
    }

Upvotes: 2

Views: 73

Answers (1)

Majed Badawi
Majed Badawi

Reputation: 28414

A better way to do this would be using HashMap to achieve a linear time complexity, where you would iterate over the array, save the # of occurrences of each item, and return a list of those that occur the most:

private static List<Integer> getMostFreq(int[] arr){
        List<Integer> list = new ArrayList<>();
        if(arr == null || arr.length == 0)
            return list;
        HashMap<Integer, Integer> map = new HashMap<>();
        for(int num : arr)
            if(!map.containsKey(num))
                map.put(num,1);
            else
                map.replace(num, map.get(num)+1);
        int max = Integer.MIN_VALUE;
        for(HashMap.Entry<Integer,Integer> item : map.entrySet())
            if(item.getValue() > max)
                max = item.getValue();
        for(HashMap.Entry<Integer,Integer> item : map.entrySet())
            if(item.getValue() == max)
                list.add(item.getKey());
        return list;
}

Upvotes: 1

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