leetcode problem 848 shifting letters

Question Description

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:

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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

Solution

Approach1 :

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class  {
public String shiftingLetters(String S, int[] shifts) {
char[] sToCharArray = S.toCharArray();
int sum = 0;
for (int i = shifts.length - 1; i >= 0; i--) {
sum += shifts[i];
sum %= 'z' - 'a' + 1;
sToCharArray[i] += sum;
sToCharArray[i] = (char) (sToCharArray[i] > 'z' ? sToCharArray[i] - ('z' - 'a' + 1) : sToCharArray[i]);
}
return new String(sToCharArray);
}
}