n 個のバイナリ文字列を追加しますか?

Input: "1011", "10", "1001"
Output: 10110

#include<iostream>
using namespace std;
string add(string b1, string b2) {
   string res = "";
   int s = 0;
   int i = b1.length() - 1, j = b2.length() - 1;
   while (i >= 0 || j >= 0 || s == 1) {
      if(i >= 0) {
         s += b1[i] - &#39;0&#39;;
      } else {
         s += 0;
      }
      if(j >= 0) {
         s += b2[j] - &#39;0&#39;;
      } else {
         s += 0;
      }
      res = char(s % 2 + &#39;0&#39;) + res;
      s /= 2;
      i--; j--;
   }
   return res;
}
string addbinary(string a[], int n) { string res = "";
   for (int i = 0; i < n; i++) {
      res = add(res, a[i]);
   }
   return res;
}
int main() {
   string arr[] = { "1011", "10", "1001" };
   int n = sizeof(arr) / sizeof(arr[0]);
   cout << addbinary(arr, n) << endl;
}