interviews/leetcode/hash-table/GroupShiftedStrings.java at master · forkedjava/interviews

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// 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"]

// ]

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);

}

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

}

for(String key : map.keySet()) {

List<String> list = map.get(key);

Collections.sort(list);

result.add(list);

}

return result;

}

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