map更新或插入数据

//参考effective STL 24
#include <iostream>
#include <map>
using namespace std;

template<typename MapType, typename KeyArgType, typename ValueArgType>
typename MapType::iterator addOrUpdate(MapType &m, const KeyArgType &k, const ValueArgType &v)
{
	typename MapType::iterator lb = m.lower_bound(k);

	if ( lb != m.end() && !(m.key_comp()(k, lb->first)) )	//key_comp() 默认 std::less<Key>
	{
		lb->second = v;
		return lb;
	}
	else
	{
		typedef typename MapType::value_type MVT;
		//hint insert 常数时间
		return m.insert(lb, MVT(k, v));
	}
}

int main()
{
	map<int, string> m;
	m.insert(make_pair(1, "1"));
	m.insert(pair<int, string>(2, "2"));
	m.insert(map<int, string>::value_type(3, "3") );
	addOrUpdate(m, 4, "4");
	addOrUpdate(m, 1, "11");
	//1 "11"
	//2 "2"
	//3 "3"
	//4 "4"
	return 0;
}