GroupShiftedStrings.java

class Solution {
	public List<List<String>> groupStrings(String[] list) {
		Map<String, List<String>> m = new HashMap<>(); 
		
		for (String s : list) {
			String key = convert(s);
			if (!m.containsKey(key)) {
				m.put(key, new ArrayList<>());
			}
			
			m.get(key).add(s);
		}
		
		List<List<String>> result = new ArrayList<>(); 
		for (String key : m.keySet()) {
			result.add(m.get(key));
		}
		
		return result; 
	}
	
	private String convert(String s) {
		String res = ""; 
		char[] arr = s.toCharArray();
		
		for (int i = 1; i < arr.length; i++) {
			if (arr[i] >= arr[i - 1]) {
				res += String.valueOf((int)(arr[i] - arr[i - 1]));
			} else {
				res += String.valueOf((int)(26 + arr[i] - arr[i - 1]));;
			}
		}
		
		return res; 
	}
}