Shifting Letters II Python Solution with Tests

lcpy gen -n 2381   # by problem number
lcpy gen -s shifting_letters_ii   # by problem name

Input: s = "abc", shifts = [[0,1,0],[1,2,1],[0,2,1]]
Output: "ace"
Explanation: Firstly, shift the characters from index 0 to index 1 backward. Now s = "zac".
Secondly, shift the characters from index 1 to index 2 forward. Now s = "zbd".
Finally, shift the characters from index 0 to index 2 forward. Now s = "ace".

Input: s = "dztz", shifts = [[0,0,0],[1,1,1]]
Output: "catz"
Explanation: Firstly, shift the characters from index 0 to index 0 backward. Now s = "cztz".
Finally, shift the characters from index 1 to index 1 forward. Now s = "catz".

class Solution:
    # Time: O(n + m)
    # Space: O(n)
    def shifting_letters(self, s: str, shifts: list[list[int]]) -> str:
        diff = [0] * (len(s) + 1)
        for start, end, direction in shifts:
            offset = 1 if direction == 1 else -1
            diff[start] += offset
            diff[end + 1] -= offset

        result: list[str] = []
        running = 0
        for i, char in enumerate(s):
            running += diff[i]
            result.append(chr((ord(char) - ord("a") + running) % 26 + ord("a")))
        return "".join(result)