challenge_stl.cc

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

using namespace std;


template <typename T>
struct MyAllocator : public std::allocator<T>
{
  //MyAllocator is a customized allocator. We may add some functions in the future.
};


struct Person
{
  string name;
  int    age;
  int    height;  //cm
  float  weight;  //kg
};


class Roster
{
public:
  bool add(const Person &p)
  {
    auto result = persons_.insert(std::make_pair(p.name, p));
    return result.second;
  }

  void addBatch(const vector<Person> &persons)
  {
    for (auto &p : persons) {
      this->add(p);
    }
  }

  bool del(const string &name)
  {
    auto it = persons_.find(name);
    if (it != persons_.end()) {
      persons_.erase(it);
      return true;
    }
    return false;
  }

  template <typename Pred>
  int delIf(Pred pred)
  {
    int cnt = 0;
    auto it  = persons_.begin(),
         ite = persons_.end();
    while( it!=ite ) {
      if (pred(it->second)) {
        persons_.erase(it);
        ++cnt;
      }
      ++it;
    }
    return cnt;
  }

  void show(ostream &os)
  {
    for (auto &kv : persons_){
      os << kv.first << endl;
    }
  }

private:
  std::map<string, Person> persons_;
};


int main(int argc, const char *argv[])
{
  Person p1{"Gary", 40, 170, 65.5};
  Person p2{"Linda", 30, 160, 55.2};
  Person p3{"Jack", 35, 165, 60.5};
  Person p4{"Lucy", 28, 170, 55.0};

  vector<Person, MyAllocator<Person>> persons{p1, p2, p3};

  Roster roster;
  roster.addBatch(persons);

  roster.show(cout);
  roster.delIf([](const Person &p) { return p.age <=30; });

  return 0;
}