[LeetCode] Problem 848 - Shifting Letters

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We have a string S of lowercase letters, and an integer array shifts.

Call the shift of a letter, the next letter in the alphabet, (wrapping around so that ‘z’ becomes ‘a’).

For example, shift(‘a’) = ‘b’, shift(‘t’) = ‘u’, and shift(‘z’) = ‘a’.

Now for each shifts[i] = x, we want to shift the first i+1 letters of S, x times.

Return the final string after all such shifts to S are applied.

Example

Input: S = “abc”, shifts = [3,5,9]

Output: “rpl”

Explanation:
We start with “abc”.
After shifting the first 1 letters of S by 3, we have “dbc”.
After shifting the first 2 letters of S by 5, we have “igc”.
After shifting the first 3 letters of S by 9, we have “rpl”, the answer.

Note

  1. 1 <= S.length = shifts.length <= 20000
  2. 0 <= shifts[i] <= 10 ^ 9

Code

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public String shiftingLetters(String S, int[] shifts) {
    char[] ch = S.toCharArray();
    int shift = 0;

    for (int i = shifts.length - 1; i >= 0; i--) {
        shift += shifts[i] % 26;
        ch[i] = (char) ('a' + (ch[i] - 'a' + shift) % 26);
    }   
    
    return String.valueOf(ch);
}