Problem

Given a string S, return the "reversed" string where all characters that are not a letter stay in the same place, and all letters reverse their positions.

Example 1:Input: "ab-cd"Output: "dc-ba"Example 2:Input: "a-bC-dEf-ghIj"Output: "j-Ih-gfE-dCba"Example 3:Input: "Test1ng-Leet=code-Q!"Output: "Qedo1ct-eeLg=ntse-T!"

Note:

S.length <= 10033 <= S[i].ASCIIcode <= 122 S doesn't contain \ or "

Solution

class Solution {    public String reverseOnlyLetters(String S) {        char[] str = S.toCharArray();        int i = 0, j = str.length-1;        while (i < j) {            while (i < j && !Character.isLetter(str[i])) i++;            while (i < j && !Character.isLetter(str[j])) j--;            swap(str, i++, j--);        }        StringBuilder sb = new StringBuilder();        sb.append(str);        return sb.toString();    }    private void swap(char[] str, int i, int j) {        char temp = str[i];        str[i] = str[j];        str[j] = temp;    }}