LintCode-Sort Letters by Case

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

Note

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"

Solution:

public class Solution {
    /**
     *@param chars: The letter array you should sort by Case
     *@return: void
     */
    public void sortLetters(char[] chars) {
        int len = chars.length;
        if (len <= 1) return;

        int p1 = 0, p2 = len-1;
        while (p1<len && chars[p1]>='a' && chars[p1]<='z') p1++;
        while (p2>=0 && chars[p2]>='A' && chars[p2]<='Z') p2--;
        while (p1<p2){
            //swap p1 and p2.
            char temp = chars[p1];
            chars[p1] = chars[p2];
            chars[p2] = temp;
            //find next swap positions.
            while (p1<len && chars[p1]>='a' && chars[p1]<='z') p1++;
            while (p2>=0 && chars[p2]>='A' && chars[p2]<='Z') p2--;
        }
    }
}