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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

求解

class Solution {
    public String stringShift(String s, int[][] shift) {
        int headIndex = 0;
        int shiftCount = 0;
        for (int i = 0; i < shift.length ; i++) {
            if (shift[i][0] == 0){
                shiftCount += shift[i][1];  //headIndex + 1
            }else {
                shiftCount -= shift[i][1];
            }
        }
        char[] arr = s.toCharArray();
        headIndex = (headIndex+shiftCount + arr.length * 100) % arr.length;
        StringBuilder res = new StringBuilder();
        for (int i = headIndex; i < arr.length; i++) {
            res.append(arr[i]);
        }
        for (int i = 0; i < headIndex; i++) {
            res.append(arr[i]);
        }
        return res.toString();
    }
    public static void main(String[] args) {
        // "cab"
      //  System.out.println((new Solution()).stringShift(new String("abc"), new int[][]{{0,1},{1,2}}));
        // "efgabcd"
     //   System.out.println((new Solution()).stringShift(new String("abcdefg"), new int[][]{{1,1},{1,1},{0,2},{1,3}}));
        System.out.println((new Solution()).stringShift(new String("yzeuobhwxatulpruiab"), new int[][]{{1,15},{0,18},{0,12},{0,7},{0,7},{1,17},{1,15},{0,9},{1,4},{0,19},{1,16},{0,7},{1,4},{1,17},{1,19},{1,10},{1,2},{0,18},{1,15}}));
    }
}