Sort Letters by Case

Sort Letters by Case (leetcodelintcode)

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

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

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

Challenge 
Do it in one-pass and in-place.

解题思路

思路与 Partition Array 相同，使用指向数组首尾的双指针，向中间遍历。

易错点

1. Character.isLowerCase() 函数的使用。

Java 实现

public
class
Solution
{

/** 
     *
@param
 chars: The letter array you should sort by Case
     *
@return
: void
     */
public
void
sortLetters
(
char
[] chars)
{

if
 (chars == 
null
 || chars.length == 
0
) {

return
;
        }


int
 left = 
0
;

int
 right = chars.length - 
1
;

while
 (left 
<
= right) {

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

while
 (left 
<
= right 
&
&
 Character.isUpperCase(chars[right])) {
                right--;
            }


if
 (left 
<
= right) {

char
 temp = chars[left];
                chars[left] = chars[right];
                chars[right] = temp;
            }
        }

return
;
    }
}