find nearest value

finddr.cpp

#include <iostream>
#include <queue>

int main() {
  struct DrInfo {
    int64_t timestamp;
  };
  std::queue<DrInfo> dr_queue_;
  std::queue<DrInfo> dr_queue2_;

  DrInfo dr_data;
  dr_data.timestamp = 179;
  dr_queue_.push(dr_data);

  dr_data.timestamp = 184;
  dr_queue_.push(dr_data);

  dr_data.timestamp = 192;
  dr_queue_.push(dr_data);

  dr_data.timestamp = 197;
  dr_queue_.push(dr_data);

  dr_queue2_ = dr_queue_;

  int64_t ref_time = 186;

  /// -------------------------------
  {
    DrInfo current;
    while (!dr_queue_.empty()) {
      current = dr_queue_.front();
      if (current.timestamp < ref_time && dr_queue_.size() > 1) {
        dr_queue_.pop();
      } else {
        break;
      }
    }

    if (!dr_queue_.empty()) {
      printf("\t%lld\n", current.timestamp);
    }
  }

  /// -------------------------------
  {
    DrInfo ldr, rdr;
    const int64_t init_v = 123456789;
    int64_t left_diff = init_v, right_diff = -init_v;
    while (!dr_queue2_.empty()) {
      const auto& dr = dr_queue2_.front();
      if (dr.timestamp < ref_time) {
        left_diff = dr.timestamp - ref_time;
        ldr = dr;
        dr_queue2_.pop();
      } else {
        rdr = dr;
        right_diff = dr.timestamp - ref_time;
        break;
      }
    }

    if (abs(left_diff) < right_diff)
      printf("\t%lld\n", ldr.timestamp);

    else if (abs(left_diff) == init_v)
      printf("\t%lld\n", rdr.timestamp);

    else if (abs(right_diff) == init_v)
      printf("\t%lld\n", ldr.timestamp);
  }

  return 0;
}