Find the N Most Frequent Elements in a Java Array

Find the N Most Frequent Elements in a Java Array

Working with arrays in Java can be tricky, but finding the N most frequent elements in a Java Array is surprisingly straightforward. In this article, we'll explore a few methods for accomplishing this task. By the end of this article, you'll be ready to tackle any array-related problem that comes your way.

Iteration Method

The first method we'll look at is the Iteration Method. This is a very basic approach to solving this problem and requires looping through the entire array, keeping track of the frequency of each element. To keep track of the frequency of each element, we'll need to declare an int array of size equal to the number of distinct elements in the original array. Then, we'll increment the appropriate index in the int array by one every time we encounter the same element in the original array. Once we have finished looping, we can then sort the int array in descending order and use the top N elements to determine the N most frequent elements in the original array.

Hash Map Method

The second method we'll look at is the Hash Map Method. This is a much more efficient approach to solving this problem and requires using a Hash Map to keep track of the frequency of each element. First, we'll need to declare a Hash Map object where the key is the element and the value is the frequency of that element. Then, we'll loop through the entire array and add each element to the Hash Map as a key with an initial value of one. If the element already exists in the Hash Map, we’ll simply increment its value by one. Once we have finished looping, we can then sort the Hash Map by value in descending order and use the top N entries to determine the N most frequent elements in the original array.

Conclusion

Finding the N most frequent elements in a Java Array is a fairly simple task that can be accomplished using a variety of methods. The two methods explored in this article are the Iteration Method and the Hash Map Method. Both methods result in the same outcome but the latter is much more efficient and should be used whenever possible. Try these methods out for yourself, and see how easy it is to find the N most frequent elements in a Java Array!