构造限制重复的字符串

/*
 * 思路：
 * 1. 使用Stream对字符串s的字符进行排序，并计数。
 * 2. 遍历排序后的字符，并按repeatLimit的要求构造结果字符串。
 */

import java.util.*;
import java.util.stream.Collectors;

public class Solution {
    public String repeatLimitedString(String s, int repeatLimit) {
        // 获取字符频率和字典序排序的列表
        List<Map.Entry<Character, Long>> sortedEntries = s.chars()
                .mapToObj(c -> (char) c)
                .collect(Collectors.groupingBy(c -> c, Collectors.counting()))
                .entrySet()
                .stream()
                .sorted((a, b) -> b.getKey().compareTo(a.getKey()))
                .collect(Collectors.toList());
        
        StringBuilder result = new StringBuilder();
        
        for (int i = 0; i < sortedEntries.size(); i++) {
            Map.Entry<Character, Long> entry = sortedEntries.get(i);
            char current = entry.getKey();
            long freq = entry.getValue();
            long count = Math.min(freq, repeatLimit);
            for (int j = 0; j < count; j++) {
                result.append(current);
            }
            sortedEntries.set(i, Map.entry(current, freq - count));
            if (freq - count > 0) {
                if (i + 1 < sortedEntries.size()) {
                    result.append(sortedEntries.get(i + 1).getKey());
                    long nextFreq = sortedEntries.get(i + 1).getValue() - 1;
                    if (nextFreq > 0) {
                        sortedEntries.set(i + 1, Map.entry(sortedEntries.get(i + 1).getKey(), nextFreq));
                    } else {
                        i++; // skip the next entry
                    }
                    i--; // reprocess the current entry
                }
            }
        }
        return result.toString();
    }
}