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Perform String Shifts

Created: April 14, 2020 by [lek-tin]

Last updated: April 14, 2020

You are given a string s containing lowercase English letters, and a matrix shift, where shift[i] = [direction, amount]:

• direction can be 0 (for left shift) or 1 (for right shift).
• amount is the amount by which string s is to be shifted.
• A left shift by 1 means remove the first character of s and append it to the end.
• Similarly, a right shift by 1 means remove the last character of s and add it to the beginning.
• Return the final string after all operations.

Example 1

Input: s = "abc", shift = [[0,1],[1,2]]
Output: "cab"
Explanation: 
[0,1] means shift to left by 1. "abc" -> "bca"
[1,2] means shift to right by 2. "bca" -> "cab"

Example 2

Input: s = "abcdefg", shift = [[1,1],[1,1],[0,2],[1,3]]
Output: "efgabcd"
Explanation:  
[1,1] means shift to right by 1. "abcdefg" -> "gabcdef"
[1,1] means shift to right by 1. "gabcdef" -> "fgabcde"
[0,2] means shift to left by 2. "fgabcde" -> "abcdefg"
[1,3] means shift to right by 3. "abcdefg" -> "efgabcd"

Constraints

1. 1 <= s.length <= 100
2. s only contains lower case English letters.
3. 1 <= shift.length <= 100
4. shift[i].length == 2
5. 0 <= shift[i][0] <= 1
6. 0 <= shift[i][1] <= 100

Solution

class Solution:
    def stringShift(self, s: str, shift: List[List[int]]) -> str:
        offset = 0
        N = len(s)

        for sh in shift:
            offset += sh[1] if sh[0] > 0 else -sh[1]
            offset %= N

        res = ""
        for i in range(len(s)):
            res += s[(-offset+i)%N]

        return res