How to use map and what effect it is.

c++_stl_map.cc

#include<iostream>
#include<map>
#include<functional>

using namespace std;

//print map element
void print(map<int, char> m)
{
	//empth function
	if (m.empty())//nothing in the m
	{
		cout << "nothing" << endl;
		return;
	}

	//using iterator
	map<int, char>::iterator iter;
	for (iter = m.begin(); iter != m.end(); ++iter)
	{
		cout << iter->first << " " << iter->second << endl;
	}
	cout << endl;
}

int main()
{
	map<int, char> m; //key type : int, value type : char
	
    //Insert (1,'a') to map
	printf("insert (1,a)\n");
	m[1] = 'a'; //If a key value of 1 exists, it is updated. Otherwise, add to map.
	print(m);
	
	//insert function
	pair<map<int, char>::iterator, bool> success;
	success = m.insert(pair<int, char>(0, 'b')); //If it succeeds, return true. Otherwise return false. 
	if (success.second == true)
		printf("insert (%d,%c)\n", success.first->first, success.first->second);
	pair<int, char> temp; //Create an object to insert first
	temp = make_pair(2, 'c');
	m.insert(temp);
	printf("insert (2,c)\n");
	print(m);

	//count
	cout << "m.count(1) : " << m.count(1) << endl; //Number of key values in map 1
	cout << "m.count(5) : " << m.count(5) << endl; //Number of key values in map 5

	//emplace
	cout << endl << "m.emplace (3,e)" << endl;
	m.emplace(pair<int, char>(3, 'e'));
	print(m);

	//erase
	cout << "erase(3)"<<endl;
	m.erase(3);
	print(m);

	//find,lower_bound, upper_bound,
	map<int, char>::iterator iter;
	iter = m.find(1);
	if(iter==m.end())
		printf("Can not find(1)\n\n");
	else
		printf("find(1) : %c\n\n", iter->second);

	map<int, char>::iterator upp;
	map<int, char>::iterator low;
	low = m.lower_bound(1);
	upp = m.upper_bound(1);
	printf("lower_bound(1) : (%d, %c)\n", low->first, low->second);
	printf("upper_bound(1) : (%d, %c)\n", upp->first, upp->second);
	cout << endl;

	//size
	cout<<"size of map : "<<m.size()<<endl;
	cout << endl;

	//greater sort
	map<int, char, greater<int>> gre;
	for (int i = 0; i < m.size(); i++)
		gre[i] = m[i];
	map<int, char, greater<int>> ::iterator iter2;
	cout << "greater<int>" << endl;
	for (iter2 = gre.begin(); iter2 != gre.end(); ++iter2)
	{
		cout << iter2->first << " " << iter2->second << endl;
	}
	cout << endl;

	//print reverse
	map<int, char> ::reverse_iterator riter;
	cout << "print reverse" << endl;
	for (riter = m.rbegin(); riter != m.rend(); ++riter)
		cout << riter->first << " " << riter->second << endl;
	cout << endl;

	//swap
	map<int, char> m2;
	m2[0] = 'z';
	m.swap(m2);
	cout << "swap(m2)" << endl;
	print(m);

	//clear
	cout << "clear map" << endl;
	m.clear();
	print(m);

	return 0;
}