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 <= S.length = shifts.length <= 20000
0 <= shifts[i] <= 10 ^ 9
class Solution {
public String shiftingLetters(String S, int[] shifts) {
if(S==null||S.isEmpty())
return S;
StringBuilder sb=new StringBuilder(S);
for(int i=0;i<sb.length();i++){
for(int j=0;j<=i;j++){
sb.setCharAt(j,(char)(((sb.charAt(j)-'a'+shifts[i])%26+'a')));
}
}
return sb.toString();
}
}
这道题使用StringBuffer时 时间超过限制Time Limit Exceeded,使用StringBuilder才能通过,通过的思路是在遍历shifts的时候,将它加到i之前的所有已经遍历过的字符上。