Hyper Log Log Sketch C++ Example

#include <iostream>
#include <fstream>

#include <hll.hpp>

//simplified file operations and no error handling for clarity
int main(int argc, char **argv) {
  const int lg_k = 11;
  const auto type = datasketches::HLL_4; // this is the default, but explicit here for illustration

  // this section generates two sketches with some overlap and serializes them into files
  {
    // 100000 distinct keys
    datasketches::hll_sketch sketch1(lg_k, type); // type is optional, defaults to HLL_4
    for (int key = 0; key < 100000; key++) sketch1.update(key);
    std::ofstream os1("hll_sketch1.bin");
    sketch1.serialize_compact(os1);

    // 100000 distinct keys
    datasketches::hll_sketch sketch2(lg_k, type); // type is optional, defaults to HLL_4
    for (int key = 50000; key < 150000; key++) sketch2.update(key);
    std::ofstream os2("hll_sketch2.bin");
    sketch2.serialize_compact(os2);
  }

  // this section deserializes the sketches, produces union and prints the result
  {
    std::ifstream is1("hll_sketch1.bin");
    auto sketch1 = datasketches::hll_sketch::deserialize(is1);

    std::ifstream is2("hll_sketch2.bin");
    auto sketch2 = datasketches::hll_sketch::deserialize(is2);

    datasketches::hll_union u(lg_k);
    u.update(sketch1);
    u.update(sketch2);
    auto sketch = u.get_result(type); // type is optional, defaults to HLL_4

    // debug summary of the union result sketch
    std::cout << sketch.to_string();

    std::cout << "Distinct count estimate: " << sketch.get_estimate() << std::endl;
    std::cout << "Distinct count lower bound 95% confidence: " << sketch.get_lower_bound(2) << std::endl;
    std::cout << "Distinct count upper bound 95% confidence: " << sketch.get_upper_bound(2) << std::endl;
  }

  return 0;
}

### HLL SKETCH SUMMARY: 
  Log Config K   : 11
  Hll Target     : HLL_4
  Current Mode   : HLL
  LB             : 148634
  Estimate       : 152041
  UB             : 155614
  OutOfOrder flag: true
  CurMin         : 4
  NumAtCurMin    : 21
  HipAccum       : 147291
  KxQ0           : 19.889
  KxQ1           : 0
Distinct count estimate: 152041
Distinct count lower bound 95% confidence: 145234
Distinct count upper bound 95% confidence: 159184