Formatted question description: https://leetcode.ca/all/1427.html

1427. Perform String Shifts

Level

Easy

Description

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 <= s.length <= 100
  • s only contains lower case English letters.
  • 1 <= shift.length <= 100
  • shift[i].length == 2
  • 0 <= shift[i][0] <= 1
  • 0 <= shift[i][1] <= 100

Solution

Calculate the accumulated amount of shifts. If a right shift is performed, the amount is counted as a negative value. After all operations, the total amount of left shifts is calculated. If the amount is x where 0 <= x < s.length(), then the final string is s.substring(x) + s.substring(0, x). Return the final string.

class Solution {
    public String stringShift(String s, int[][] shift) {
        int totalShift = 0;
        for (int[] curShift : shift) {
            int direction = curShift[0], amount = curShift[1];
            if (direction == 1)
                amount = -amount;
            totalShift += amount;
        }
        int length = s.length();
        totalShift %= length;
        if (totalShift < 0)
            totalShift += length;
        String shifted = s.substring(totalShift) + s.substring(0, totalShift);
        return shifted;
    }
}

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