USACO 2.1 Hamming Codes

#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>

using namespace std;

int main() {
  ifstream fin("hamming.in");
  ofstream fout("hamming.out");

  int N, B, D;
  fin >> N >> B >> D;
  vector<int> result;
  result.push_back(0);
  int count = 1;
  for (int i = 1; count < N; ++i) {
    if (count == N) break;

    bool ok(true);
    for (auto &item : result) {
      bitset<64> diff(i ^ item);
      if (diff.count() < D) {
        ok = false;
        break;
      }
    }

    if (ok) {
      ++count;
      result.push_back(i);
    }
  }

  count = 0;
  for (int i = 0; i < result.size(); ++i) {
    count++;
    fout << result[i];
    if ((count != 0 && count % 10 == 0) || count == result.size())
      fout << endl;
    else
      fout << " ";
  }

  return 0;
}