How to get the most frequent 100 numbers out of 1,000,000,000 numbers in java?

How to get the most frequent 100 numbers out of 1,000,000,000 numbers in java?

To find the most frequent 100 numbers out of a large dataset of 1,000,000,000 numbers in Java, you can use a combination of data structures and algorithms to efficiently solve this problem. A common approach is to use a priority queue (min-heap) to keep track of the top 100 most frequent numbers. Here's a step-by-step guide to achieving this:

import java.util.*; public class Top100FrequentNumbers { public static List<Integer> findTop100FrequentNumbers(int[] numbers) { // Create a HashMap to store the frequency of each number Map<Integer, Integer> frequencyMap = new HashMap<>(); // Count the frequency of each number for (int num : numbers) { frequencyMap.put(num, frequencyMap.getOrDefault(num, 0) + 1); } // Create a min-heap (priority queue) to keep the top 100 frequent numbers PriorityQueue<Map.Entry<Integer, Integer>> minHeap = new PriorityQueue<>(Comparator.comparingInt(Map.Entry::getValue)); // Iterate through the frequency map and add entries to the min-heap for (Map.Entry<Integer, Integer> entry : frequencyMap.entrySet()) { minHeap.offer(entry); // If the size of the min-heap exceeds 100, remove the least frequent number if (minHeap.size() > 100) { minHeap.poll(); } } // Extract the top 100 frequent numbers from the min-heap List<Integer> top100FrequentNumbers = new ArrayList<>(); while (!minHeap.isEmpty()) { top100FrequentNumbers.add(minHeap.poll().getKey()); } // Reverse the list to get the most frequent numbers first Collections.reverse(top100FrequentNumbers); return top100FrequentNumbers; } public static void main(String[] args) { // Example: Generate an array of 1,000,000,000 random numbers (for demonstration purposes) int[] numbers = new int[1_000_000_000]; Random random = new Random(); for (int i = 0; i < numbers.length; i++) { numbers[i] = random.nextInt(1000); // Assuming numbers in the range [0, 999] } // Find the top 100 frequent numbers List<Integer> top100 = findTop100FrequentNumbers(numbers); // Print the top 100 frequent numbers System.out.println("Top 100 Most Frequent Numbers:"); System.out.println(top100); } }

Please note that generating 1,000,000,000 random numbers is a time-consuming task and may not be practical for a demonstration. In a real-world scenario, you would typically read data from a file or another data source. Additionally, the algorithm provided here is suitable for large datasets, but it may still require significant computational resources for processing such a large amount of data.

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