最大相等频率

/*
题目思路：
使用Java Stream来实现相同的功能。我们会使用map来统计出现次数和频率。
然后用filter和collect等操作来实现对频率的检查。
*/
import java.util.*;
import java.util.stream.Collectors;

public class Solution {
    public int maxEqualFreq(int[] nums) {
        Map<Integer, Integer> count = new HashMap<>();
        Map<Integer, Integer> freq = new HashMap<>();
        int maxFreq = 0;
        int res = 0;
        for (int i = 0; i < nums.length; i++) {
            int num = nums[i];
            count.merge(num, 1, Integer::sum);
            int newCount = count.get(num);
            freq.merge(newCount - 1, -1, Integer::sum);
            if (freq.get(newCount - 1) == 0) freq.remove(newCount - 1);
            freq.merge(newCount, 1, Integer::sum);
            maxFreq = Math.max(maxFreq, newCount);
            boolean valid = maxFreq == 1 || (freq.getOrDefault(maxFreq, 0) == 1 && freq.getOrDefault(maxFreq - 1, 0) * (maxFreq - 1) + maxFreq == i + 1) || (freq.getOrDefault(1, 0) == 1 && freq.get(maxFreq) * maxFreq == i);
            if (valid) res = i + 1;
        }
        return res;
    }
}