Group Shifted Strings - Python Solution Leetcode

 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 non-empty strings which contains only lowercase alphabets, group all strings that belong to the same shifting sequence.

Example:

Input: ["abc", "bcd", "acef", "xyz", "az", "ba", "a", "z"],
Output: 
[
  ["abc","bcd","xyz"],
  ["az","ba"],
  ["acef"],
  ["a","z"]
]

class Solution:
    def groupStrings(self, strings: List[str]) -> List[List[str]]:
        groups = collections.defaultdict(list)
        for s in strings:
            key = ()
            for i in range(len(s)-1):
                key += ((26+ ord(s[i+1]) - ord(s[i])) % 26,)
            groups[key] = groups.get(key,[])+[s]

        return groups.values()
                         

TC:O(no of strings * longest string length) SC: O(n) Hashmap storage.