Python 3   ||   7 lines, w/ explanation    ||   T/S: 92% / 18%
The code first splits the string s at every occurrence of the character \'a\' using the split function. This creates a list arr containing the substrings (inclu
The code first splits the string `s` at every occurrence of the character \'a\' using the split function. This creates a list arr containing the substrings (including null strings) that are between the \'a\' characters.\n\nNext, the code iterates over the elements of `arr`. It checks whether the current substring `ss` is non-empty. If it is, it replaces the characters in `ss` with their lexicographically smaller counterparts. This is done by converting each character to its *ASCII* value, subtracting 1, and converting it back to a character using `chr`. The modified substring is stored back in `arr[i]`, and the loop is terminated using the break statement.\n\nIf the loop completes without finding a non-empty substring, then the string`s` consists only of \'a\' characters, and, the function returns the string obtained by replacing the last character of `s` with \'z\'.\n\nFinally, the function joins the elements of `arr` back together using the letter \'a\' as a separator, and returns the resulting string. --*ChatGPT*\n```\nclass Solution:\n    def smallestString(self, s: str) -> str:\n\n        arr = s.split(\'a\')\n\n        for i, ss in enumerate(arr):\n            if ss:\n                arr[i] = \'\'.join([chr(ord(ch)-1) for ch in ss])\n                break\n\n        else: return s[:-1] + \'z\'\n        \n        return \'a\'.join(arr)\n```\n[https://leetcode.com/problems/lexicographically-smallest-string-after-substring-operation/submissions/968982692/](http://)\n\nI could be wrong, but I think that time complexity is *O*(*N*) and space complexity is *O*(*N*), in which *N* ~`len(s)`.
['Python3']