C/C++ TIPS

List some tips when using C/C++.

1. Use std::sort instead of qsort (At least, in Visual C++). This is because std::sort is faster than qsort.
2. Keys in an associative container are immutable.  Keep it in mind, expecially when you are using std::set and std::multiset.  Also, iterator and const_iterator for std::set and std::multiset are both constant iterators.  (VC9 SP1 doesn't follow the rules, VC10 will enforce these rules) [N2798.pdf]
   • )23.1.4/5 For set and multiset the value type is the same as the key type. For map and multimap it is equal to pair<const Key, T>. Keys in an associative container are immutable.
   • )23.1.4/6 Iterator of an associative container meets the requirements of the BidirectionalIterator concept. For associative containers where the value type is the same as the key type, both iterator and const_iterator are constant iterators. It is unspecified whether or not iterator and const_iterator are the same type.
3. When seq is a vector, deque or list, please don't write this:
       copy(first, last, back_inserter(seq));
   instead, write this:
       seq.insert(seq.end(), first, last);
   That's not only slightly less typing, it's also significantly more efficient.  (copy()-to-back_inserter() performs repeated push_back()s and hence can trigger multiple vector reallocations, whereas insert()-at-end() will perform at most one vector reallocation. deque also benefits.)
4. The member variables are initialized by the order that they are declared (not the order they appear in the constructor initialization list) and nothing to do with the access modifiers (public, protected and private).