使数组元素相等的减少操作次数

/*
 * 思路：
 * 1. 统计每个数的频率，并按从大到小排序。
 * 2. 使用Java Stream API实现上面的逻辑。
 */

import java.util.Arrays;
import java.util.Map;
import java.util.stream.Collectors;

public class MakeElementsEqualStream {
    public int reductionOperations(int[] nums) {
        Map<Integer, Long> freq = Arrays.stream(nums)
                .boxed()
                .collect(Collectors.groupingBy(e -> e, Collectors.counting()));

        int[] uniqueNums = freq.keySet().stream().sorted().mapToInt(e -> e).toArray();

        int operations = 0;
        for (int i = uniqueNums.length - 1; i > 0; i--) {
            operations += freq.get(uniqueNums[i]) * (i);
            freq.put(uniqueNums[i - 1], freq.get(uniqueNums[i - 1]) + freq.get(uniqueNums[i]));
        }

        return operations;
    }

    public static void main(String[] args) {
        MakeElementsEqualStream solution = new MakeElementsEqualStream();
        int[] nums1 = {5, 1, 3};
        System.out.println(solution.reductionOperations(nums1)); // 输出: 3
        int[] nums2 = {1, 1, 1};
        System.out.println(solution.reductionOperations(nums2)); // 输出: 0
        int[] nums3 = {1, 1, 2, 2, 3};
        System.out.println(solution.reductionOperations(nums3)); // 输出: 4
    }
}