将数组划分成相等数对

/*
 * Problem: Given an array nums containing 2 * n integers, 
 * you need to check if it can be divided into n pairs of equal elements. 
 * Return true if possible, otherwise return false.
 * 
 * Approach using Java Streams: 
 * 1. Use a HashMap to count the frequency of each element in the array.
 * 2. Utilize Java Streams to count frequencies and check if all are even.
 */

import java.util.HashMap;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class Solution {
    public boolean canFormPairs(int[] nums) {
        HashMap<Integer, Integer> freqMap = new HashMap<>();
        // Count frequencies using Streams
        IntStream.of(nums).forEach(num -> freqMap.put(num, freqMap.getOrDefault(num, 0) + 1));
        // Check if all counts are even using Streams
        return freqMap.values().stream().allMatch(count -> count % 2 == 0);
    }
}