GroupAnagrams.java

// https://leetcode.com/problems/group-anagrams/
// #hash-table #string
class Solution {
  public List<List<String>> groupAnagrams(String[] strs) {
    HashMap<String, List<String>> map = new HashMap<>();
    List<List<String>> result = new ArrayList<>();
    for (String s : strs) {
      int[] ca = new int[27];
      for (int k = 0; k < s.length(); k++) {
        ca[(int) (s.charAt(k) - 'a' + 1)]++;
      }
      StringBuilder sb = new StringBuilder();
      for (int k = 1; k < ca.length; k++) {
        sb.append(ca[k] + "#");
      }
      String key = sb.toString();
      if (map.containsKey(key)) {
        map.get(key).add(s);
      } else {
        List<String> ls = new ArrayList<>();
        ls.add(s);
        map.put(key, ls);
        result.add(ls);
      }
    }

    return result;
  }
}