Creating a list of keys from an STL map.

keys.cpp

/**
 * Creating a list of keys from an STL map.
 *
 * Build: g++ -o keys keys.cpp
 *   Run: ./keys
 */

#include <iostream>
#include <map>
#include <string>
#include <vector>

// Fake ClassifierResult container for demonstration purposes
struct ClassifierResult {
  int a;
};

int main(int argc, char* argv[]) {
  // Build a fake map of fake ClassifierResults
  std::map<std::string, ClassifierResult> fClassifierResults;
  fClassifierResults["foo"] = ClassifierResult();
  fClassifierResults["bar"] = ClassifierResult();

  // Create a vector of the keys
  // Note that STL maps are generally sorted ascending by key
  std::vector<std::string> keys;
  std::map<std::string, ClassifierResult>::iterator it;
  for (it=fClassifierResults.begin(); it!=fClassifierResults.end(); ++it) {
    keys.push_back(it->first);
  }

  // Print it
  for (size_t i=0; i<keys.size(); i++) {
    std::cout << keys[i] << std::endl;
  }

  return 0;
}