leetcode讲解–917. Reverse Only Letters

题目
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 <= 100
33 <= S[i].ASCIIcode <= 122

S doesn’t contain \ or ”

讲解
字符串操作，将字母reverse，其他字符保持在原来位置上。我使用了两个数组，一个指针
java代码
class Solution {
public String reverseOnlyLetters(String S) {
char[] c = S.toCharArray();
char[] result = S.toCharArray();
int index = result.length-1;
for(int i=0;i<c.length;i++){
if(c[i]>=’a’ && c[i]<=’z’ || c[i]>=’A’ && c[i]<=’Z’){
while(index>=0 && !(result[index]>=’a’ && result[index]<=’z’ || result[index]>=’A’ && result[index]<=’Z’)){
index–;
}
if(index>=0)
result[index–] = c[i];
}
}
return String.valueOf(result);
}
}