唯一类别的数量

/*
 * LeetCode 2782: Unique Number of Occurrences
 * Given an array of integers, write a function that returns the number of unique values in the array.
 * 
 * Approach using Java Streams:
 * 1. Use streams to count the frequency of each element in the array and store it in a Map.
 * 2. Use a Set to store the frequencies to ensure they are unique.
 * 3. If the size of the Set is equal to the number of unique elements in the array, return true; otherwise, return false.
 */
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class SolutionStream {
    public boolean uniqueOccurrences(int[] arr) {
        // Step 1: Use streams to count the frequency of each element
        var frequencyMap = IntStream.of(arr)
            .boxed()
            .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

        // Step 2: Use a Set to store the frequencies
        var frequencySet = new HashSet<>(frequencyMap.values());

        // Step 3: Compare the size of the Set and the frequencyMap values
        return frequencySet.size() == frequencyMap.size();
    }
}