# Group Shifted Strings

Group Shifted Strings hash table

Given a string, we can “shift” each of its letter to its successive letter, for example: “abc” -> “bcd”. We can keep “shifting” which forms the sequence:

``````"abc" -> "bcd" -> ... -> "xyz"
``````

Given a list of strings which contains only lowercase alphabets, group all strings that belong to the same shifting sequence.

``````For example, given: ["abc", "bcd", "acef", "xyz", "az", "ba", "a", "z"],
A solution is:

[
["abc","bcd","xyz"],
["az","ba"],
["acef"],
["a","z"]
]
``````

Group Shifted Strings Solution

``````public class GroupShiftedStrings {
public List<List<String>> groupStrings(String[] strings) {
List<List<String>> result = new ArrayList<List<String>>();

HashMap<String, List<String>> map = new HashMap<String, List<String>>();

for(String s : strings) {
int offset = s.charAt(0) - 'a';
String key = "";

for(int i = 0; i < s.length(); i++) {
char current = (char)(s.charAt(i) - offset);

if(current < 'a') {
current += 26;
}

key += current;
}

if(!map.containsKey(key)) {
List<String> list = new ArrayList<String>();
map.put(key, list);
}

}

for(String key : map.keySet()) {
List<String> list = map.get(key);

Collections.sort(list);