Max continuous ones in binary representation of a number

This problem was asked by Stripe.

Given an integer n, return the length of the longest consecutive run of 1s in its binary representation.

For example, given 156, you should return 3

My Solution(C++):

#include <iostream>
#include <string>
#include <algorithm>

std::string convertBinary(int n){
  std::string bin = "";
  while (n>0){
    if (n%2==1) bin.push_back('1');
    else bin.push_back('0');
    n/=2;
  }
  std::reverse(bin.begin(), bin.end());
  return bin;
}

int countMaxContinuousOnes(int n){
  std::string binString = convertBinary(n);
  // std::cout<<binString<<'\n';
  int len = binString.length(), i = 0, maxCount = 0;
  while (i<len){
    // std::cout<<"I = "<<i<<'\n';
    int j = i;
    while(binString.at(j)=='1') {
      // std::cout<<"J = "<<j<<'\n';
      j++;
    }
    // std::cout<<"J-I = "<<j-i<<'\n';
    if (maxCount<j-i) maxCount = j-i;
    i = j+1;
  }
  return maxCount;
}

void test(){
  std::cout<<countMaxContinuousOnes(156)<<'\n';
}

int main(){
  test();
  return 0;
}