字母异位词分组

/**

 * 排序

 *

 * @param strs

 * @return

 */

public static List<List<String>> groupAnagrams(String[] strs) {

    Map<String, List<String>> maps = new HashMap<>();

    for (String s : strs){

        // 将单词中的字母排序，得到一个 key 值

        char[] chars = s.toCharArray();

        Arrays.sort(chars);

        String value = Arrays.toString(chars);

        if (!maps.containsKey(value)){

            maps.put(value, new ArrayList<>());

        }

        maps.get(value).add(s);

    }

    return new ArrayList<>(maps.values());

    // 简写

	// return new ArrayList<>(Arrays.stream(strs).collect(Collectors.groupingBy(s -> s.chars().sorted().collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append).toString())).values());

}

/**

 * 计数

 *

 * @param strs

 * @return

 */

public static List<List<String>> groupAnagrams(String[] strs) {

    Map<String, List<String>> maps = new HashMap<>();

    for (String s : strs){

        int[] count = new int[26];

        // 算出每个单词中字母的个数

        for (int i = 0; i < s.length(); i++){

            count[s.charAt(i) - 'a']++;

        }

        // 将单词中字母的数量与字母为 key 值

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < 26; i++){

            if (count[i] != 0) sb.append(count[i]).append((char) 'a' + i);

        }

        String key = sb.toString();

        maps.putIfAbsent(key, new ArrayList<>());

        maps.get(key).add(s);

    }

    return new ArrayList<>(maps.values());

}