C/C++에서 모음과 자음 문자열을 교대로 사용하기

Input: abce
Output: abec

#include <iostream>
using namespace std;
bool isVowel(char ch) {
   if (ch == &#39;a&#39; || ch == &#39;e&#39; || ch == &#39;i&#39; ||
      ch == &#39;o&#39; || ch ==&#39;u&#39;)
   return true;
   return false;
}
string createAltStr(string str1, string str2,
int start, int l) {
   string finalStr = "";
   for (int i=0, j=start; j<l; i++, j++)
      finalStr = (finalStr + str1.at(i)) + str2.at(j);
   return finalStr;
}
string findAltStr(string str) {
   int nv = 0, nc = 0;
   string vstr = "", cstr = "";
   int l = str.size();
   for (int i=0; i<l; i++) {
      char ch = str.at(i);
      if (isVowel(ch)) {
         nv++;
         vstr = vstr + ch;
      } else {
         nc++;
         cstr = cstr + ch;
      }
   }
   if (abs(nv-nc) >= 2)
      return "no such string";
   if (nv > nc)
      return (vstr.at(0) + createAltStr(cstr, vstr, 1, nv));
   if (nc > nv)
      return (cstr.at(0) + createAltStr(vstr, cstr, 1, nc));
   if (cstr.at(0) < vstr.at(0))
      return createAltStr(cstr, vstr, 0, nv);
   return createAltStr(vstr, cstr, 0, nc);
}
int main() {
   string str = "abde";
   cout << findAltStr(str);
   return 0;
}