Sort Letters by Case

Given a string which contains only letters. Sort it by lower case first and upper case second.

Have you met this question in a real interview? 

Yes

Example

For "abAcD", a reasonable answer is "acbAD"

Note

It's not necessary to keep the original order of lower-case letters and upper case letters.

Challenge

Do it in one-pass and in-place.

public class Solution {

    /** 

     *@param chars: The letter array you should sort by Case

     *@return: void

     */

    public void sortLetters(char[] chars) {

        //write your code here

        if(chars == null || chars.length == 0) return;

        int left = 0, right = chars.length - 1;

        

        while(left < right){

            while(left < right && Character.isLowerCase(chars[left]))left++;

            while(left < right && !Character.isLowerCase(chars[right]))right--;

            if(left < right){

                char temp = chars[left];

                chars[left] = chars[right];

                chars[right] = temp;

                left++; right--;

            }

            

        }

    }

}