README.md

848. Shifting Letters

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 1:

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

Solutions (Rust)

1. Prefix Sum

impl Solution {
    pub fn shifting_letters(s: String, shifts: Vec<i32>) -> String {
        let mut s = s.into_bytes();
        let mut shift = 0;

        for i in (0..s.len()).rev() {
            shift = (shift + shifts[i]) % 26;
            s[i] = (s[i] - b'a' + (shift as u8)) % 26 + b'a';
        }

        String::from_utf8(s).unwrap()
    }
}