Leetcode: Shifting Letters

Shifting Letters

Similar Problems:

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"
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.


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

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

  • Solution:
// Blog link: https://code.dennyzhang.com/shifting-letters
// Basic Ideas: One pass
//  From right to left
// Complexity: Time O(n), Space O(1)
func shiftingLetters(S string, shifts []int) string {
    v := 0
    for i:=len(shifts)-1; i>=0; i-- {
        v = (v+shifts[i])%26
        shifts[i] = v

    res := ""
    code := 0
    for i, ch := range S {
        code = (int(ch-'a')+shifts[i])%26
        res += string(code+int('a'))
    return res

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