49 字符大小写排序

class Solution {
public:
    /*
     * @param chars: The letter array you should sort by Case
     * @return: nothing
     */
    void sortLetters(string &chars) {
        // write your code here
         int n=chars.size();
     int i=0;//小写字母区末位的下一个位置;
     for (int j=0;j<n;j++)
     {
         if (chars[j]>=‘a‘&&chars[j]<=‘z‘)
         {
             swap(chars[i],chars[j]);
             i++;
         }
     }
    }
};