249. Group Shifted Strings

3.04 %
public List<List<String>> groupStrings(String[] strings) {
Map<String, List<String>> map = new HashMap<>();
for (String str : strings) {
map.computeIfAbsent(normalize(str), list -> new ArrayList<>()).add(str);
}
List<List<String>> result = new ArrayList<>();
for (List<String> list : map.values()) {
result.add(list);
}
return result;
}

private String normalize(String s) {
int offset = (int)(s.charAt(0) - 'a');
StringBuilder sb = new StringBuilder();
for (int i = 0; i < s.length(); i++) {
sb.append((char) ('a' + ((s.charAt(i) - offset + 26) % 26)));
}
// System.out.println(sb.toString());
return sb.toString();
}