【LeetCode 38_字符串_算术运算】Count and Say

 string countAndSay(int n)
 {
     string res;
     if (n <= )
         return res;

     res = "";
     while (n-- > ) {
         int len = res.size();
         int i, j;
         string resTmp;

         for (i = ; i < len; i = j) {
             char ch = res[i];

             for (j = i + ; j < len; ++j) {
                 if (ch != res[j])
                     break;
             }

             resTmp = resTmp + (char)(j - i + '') + ch;
         }
         res = resTmp;
     }
     return res;
 }