vector

• Use reserve when you know the vector size, it can prevent to re-allocate memory and also redundant copy

  A a, b, c;
  vector<A> v;
  v.push_back(std::move(a));
  v.push_back(std::move(b));
  v.push_back(std::move(c));
  

  It has 3 move cstor and 1+2 copy cstor

  A a, b, c;
  vector<A> v;
  v.reserve(3);
  v.push_back(std::move(a));
  v.push_back(std::move(b));
  v.push_back(std::move(c));
  

  It has 3 move cstor

• Repalce push_back with emplace_back

  class A {
    public:
        A(int a) : _a(a) { }
    private:
        int _a;
  }; 
  vector<A> v;
  v.reserve(2)
  v.push_back(A(0)); //one cstor and one copy/move cstor
  v.emaplace_back(0); //one cstor