Perform String Shifts

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

class Solution {
    public String stringShift(String s, int[][] shift) {
        int rotateCount = 0;
        
        for (int[] value : shift) {
            if (value[0] == 0) {
                rotateCount += value[1];
            } else {
                rotateCount -= value[1];
            }
        }
        rotateCount = rotateCount % s.length();
        
        if (rotateCount > 0) {
            s = leftShift(s, rotateCount);
        } else if (rotateCount < 0) {
            s = rightShift(s, -(rotateCount));
        }
        return s;
    }
    
    private static String leftShift(String s, int num) {
        return s.substring(num) + s.substring(0, num);
    }
    
    private static String rightShift(String s, int num) {
        return s.substring(s.length() - num) + s.substring(0, s.length() - num);
    }
}